This is a rustic take on the walnut tarts from the Perigord region of France. This version is extremely simple to make and is fantastic as a single serving dessert with very simple presentation. The walnuts are bathed in a caramel sauce and half are baked while the other half are served raw allowing a combination of the two flavors and textures. —Belle Année
First make the pastry.
Place all of the dry ingredients into the bowl of a food processor fitted with a metal blade and pulse about 10 times until they are well combined.
Add the 16 pieces of cold butter and pulse 10-15 times, until the butter is well mixed through the flour mixture and there are pieces sized between grains of sand and small peas.
Add the cold water all at once and pulse until the mixture comes together. Remove from the mixer and turn out onto a floured countertop. Knead for about 15 seconds, then form two equal sized discs. Wrap with plastic and refrigerate for an hour.
Toast the walnuts by placing them on a cookie sheet in the oven while it is preheating. It should only take about 10 minutes if you put them in the oven while it is cold. Keep a close eye on them though!
Warm cream by pouring it into a small saucepan over low heat. Do not let it boil.
Pour water and sugar into a medium saucepan over medium heat. Bring it up to a boil and stir frequently until the sugar completely dissolves. Once the sugar has dissolved, stop stirring but let it continue to boil. Swirl the pan as the sugar gradually caramelizes. You'll see it begin to brown.
Once the liquid sugar mixture has turned an amber color, remove it from the heat and add the warm cream. After it stops foaming, add the walnuts, salt and butter and return to low heat for 5 minutes.
Turn the heat off and make the crostada base.
Remove the two discs from the refrigerator and cut each one evenly into quarters. These are going to make up your 8 crostadas.
Preparing one crostada at a time, roll one of the 8 pieces of dough into an 8-inch circle. Place 1/4 cup of the walnut mixture into the middle of the dough and then fold the border of the dough over an inch all around to partially enclose the walnuts. Repeat for the next 7 pieces of dough.
Place the 8 crostadas in the oven and bake at 425 for 20 minutes. Remove, top with another 1/4 cup to 1/3 cup walnut topping and serve.