1. Note: I found the crust to be slightly too small for my tart pan. Next time I make this I will do 1 1/2 times the crust recipe.
2. Combine flour, cornmeal, granulated sugar, and salt. Add the cold butter cubes, then using a pastry cutter or your fingers, quickly break the butter up in the dry ingredients. You are aiming for the size of a small pea or a bit larger.
3. Work fast. Once finished rest in the fridge for several minutes (the dough not you).
4. In a small bowl whisk together water and egg yolk.
5. Remove the mixture from the fridge, add the wet ingredients all at once to the dry ingredients. Use a fork to combine. It will feel like there’s not enough wet ingredients. But it will come together, just keep going.
6. Sprinkle lightly with flour, form into a disk and wrap in plastic wrap.
7. Refrigerate dough for 1 hour. This will allow the moisture to distribute. Crust can be refrigerated for up to 24 hours.
8. When ready to roll out, unwrap the dough into tart or pie pan. Press out with fingers working quickly to not warm the butter too much. onto a lightly floured work surface. Using a floured rolling pin, roll the dough out to an 11-inch circle. If the dough starts to break up or tear as you’re rolling it, don’t panic. Simple place the dough into the tart pan and use your fingers to press it along the bottom, sides and edges.
9. Preheat oven to 350 degrees F.
10. Place in fridge for twenty minutes while the oven preheats.
11. Line the unbaked crust with a sheet of foil or parchment paper covering all sides. Fill the pan with dried beans or pie weights. Bake for 15 minutes. Rotate the pan and bake for another 15 minutes. Remove the foil and beans from the pan and bake for another 6 minutes, or until the bottom crust looks dry and the shell is a very pale golden color. Remove the pie from the oven and let the shell cool completely.
12. To make the filling combine mascarpone and sour cream. Beat together with a wooden spoon. Add honey and vanilla extract and stir to combine.
13. When the crust is completely cool, spread the filling evenly across the bottom of the tart. Arrange fruit over the filling. Glaze with jam or honey if desired before serving.
14. This tart keeps, well wrapped in the refrigerator, for up to two days. It’s best the day it is made. I would glaze it the day you serve it if you are going to glaze.