Individual Rhubarb Tarts With Pistachios, Berries, & Shortbread Crust
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Serves: makes 4 mini tarts (about 4 inches in diameter)
 
This recipe may seem like a lot of steps, but really, it's made up of three mini recipes that are each easy and delicious on their own. To make these tarts as simple as possible, I suggest doing most of the work in advance -- you can make the rhubarb filling and tart shells a day ahead, then all that's left is putting it all together!
Ingredients
For the rhubarb filling (makes about 1 cup):
  • 7oz (about 1¾ cups chopped, or 200g.) rhubarb, cut into ½ inch pieces
  • ½ cup (100g.) granulated sugar, or more to taste
  • ¼ cup water
  • 1 tsp. fresh sqeezed lemon juice, plus more to taste
  • ½ TBSP powdered fruit pectin
For the shortbread crust (makes enough for four 4inch tart shells, with some dough leftover that can be used to make cookies. You might be able to get as many as six tarts out of it, if you try. If you only want to make a couple of tarts, you can halve the recipe):
  • 1¾ sticks (14 TBSP, or 7oz.) unsalted butter, room temperature
  • ½ cup plus 1 TBSP (115g.) granulated sugar
  • 1 tsp. pure vanilla extract
  • ½ tsp. pure almond extract (optional)
  • 1¾ cups (245g) all-purpose flour
  • pinch of fine grain sea salt
  • ½-3/4 cups (2.5 - 3.5oz.) raw almonds, finely chopped (optional -- or roasted and shelled pistachios, or other nuts)
For the Italian meringue (optional -- see recipe notes):
  • 3 large egg whites (about 100ml), room temperature
  • ¾ cup (150g) granulated sugar
  • ¼ cup water
  • ½ tsp. vanilla extract
  • ¼ tsp. lemon juice (or cream of tartar)
Extras:
  • Fresh berries of choice (I used raspberries)
  • Chopped pistachios (or almonds, or other nuts)
  • A few small leaves of mint (optional)
  • Fresh whipped cream (optional, as an alternative to the Italian meringue -- see recipe notes)
Instructions
For the rhubarb filling:
  1. Combine all the ingredients in a large, non-reactive saucepan (ie., stainless steel or nonstick, NOT aluminum or cast iron as metals like these can react with the acids and create an off flavor).
  2. Place over high heat, and bring to a rolling boil, stirring frequently with a wooden spoon. Cook until the rhubarb has broken down, and there are no whole pieces still visible (about 5-8 minutes). Remove from the heat.
  3. You can leave the filling like this, or very carefully puree it with an immersion blender, or regular blender. Always use caution when pureeing hot liquids, as they have a tendency to spatter. If the rhubarb mixture is too shallow in the pot to submerge a stick blender, transfer it to a tall glass measuring cup before pureeing. You can test the puree by dipping a spoon into it and placing it in the freezer for a couple of minutes to cool. If the puree is too tart for your taste, add a bit more sugar. If you'd like it more tart, add a few more drops of lemon juice.
  4. Pour into a clean jar, let cool completely, and store in the fridge until needed. (Puree will keep for up to two weeks. Makes about 1 cup, which is about twice what you'll need for four tarts, but is delicious stirred into ice cream, yogurt, or oatmeal, too.)
For the shortbread crust:
  1. Preheat oven to 350 degrees F.
  2. In the bowl of your mixer, add the butter, sugar, vanilla, and almond extract, and mix on low until evenly combined. Add the flour, salt, and chopped nuts if using, and mix until everything is combined. If the dough seems crumbly, you may need to use your hands to bring it together. Do not over-mix. (You can also make the dough by hand, with a wooden spoon instead of a mixer.)
  3. Take a small lump of the dough and place it into a 4-inch diameter mini tart pan with removable bottom, and press the dough evenly into the bottom and sides. Try to make the dough about an ⅛th-1/4 inch thick all over. Trim any excess from the edges of the tart. Repeat with as many tarts as you'd like to make. (I made four, and had some leftover dough for making cookies later. Leftover dough can be wrapped in plastic and stored in the fridge for up to three days. If you've made the dough in advance and kept it chilled, let it sit at room temperature until it's soft enough to handle.)
  4. With the tines of a fork, prick the bottoms of the tart shells all over, and place in the refrigerator for 40-60 minutes, or until completely firm. Once the dough is thoroughly chilled, place on a baking sheet and bake for 18-20 minutes, or until the edges are golden brown and the center looks dry and lightly golden.
  5. Remove from the oven and let cool completely before filling. (Tart shells can be baked a day in advance, and once completely cooled, stored at room temperature in an airtight container or wrapped in plastic.)
For the Italian meringue:
  1. When you are ready to serve your tarts, make the meringue. Place the egg whites, lemon juice, and vanilla in the bowl of your stand mixer.
  2. In a saucepan, combine the sugar and water. Place over medium-high heat, and cover with a lid. Let cook for 2-3 minutes, then remove the lid and clip on a candy thermometer. You'll want to cook the sugar until it reaches 245 degrees F.
  3. Meanwhile, turn on the mixer to medium speed, and let the egg whites whip until they have reached soft peaks.
  4. As soon as the sugar syrup reaches 245F, remove it from the heat. With the mixer running, very slowly and carefully pour the hot sugar syrup in (if your mixer has a spatter guard, I recommend using it, or be very careful to pour near the edge of the bowl so the hot sugar doesn't land directly on the whisk). Once all the sugar is in, increase the speed to high, and whip until the meringue is glossy, and holds stiff peaks. Transfer the meringue to a piping bag, or a plastic baggy, then snip off one corner for piping. (This will make more meringue than you need, but unfortunately, it's really difficult to make it in a smaller quantity. Extra meringue can be stored in the piping bag at room temperature for up to a few hours, or in the fridge for up to a day.)
To Assemble
  1. Add about 2 TBSP of chilled rhubarb puree to the bottom of a cooled shortbread crust. Garnish with a few fresh berries, some chopped pistachios, almonds, or other nuts, and maybe a leaf or two of mint. Pipe little dollops of meringue, if you've chosen to make some, then use a kitchen torch to toast the meringue to a light golden brown. (Alternatively, you can skip the meringue all together and use fresh whipped cream instead - just don't try to torch it.) Serve!
Notes
The Italian meringue is a fun and tasty garnish, and is really quite simple to make. However, if using a stand mixer and a candy thermometer isn't your idea of fun, you can ditch the meringue and make fresh whipped cream instead. It pairs just as well with these tarts, and only takes a minute to make. Add ½ cup of heavy cream (try to find some good, local cream, as it will likely whip a lot better than the store-brand stuff), about a TBSP of sugar (more or less, to taste) and a splash of vanilla extract to a bowl. Whip with a hand or stand mixer, or do it by hand with a metal whisk (I whip cream like this on a daily basis, because it's less effort than getting out my mixer -- it's way easier than you'd expect!) Be careful not to over-whip. You can dollop the fresh whipped cream onto the tarts with a spoon, pipe it through a piping bag, or serve it on the side.

I used THESE mini tart pans, which are about 4 inches in diameter, and have a false bottom that makes the tarts very easy to remove. There are others out there that are similar, but so far I've been happy with mine.
Recipe by Will Cook For Friends at https://www.willcookforfriends.com/2016/05/individual-rhubarb-tarts-shortbread-crust.html