Mid-Summer Peach Tart with Blackberry Custard

Directions

1. Flaky Tart Dough
2. In a small bowl, combine the flour and salt.
3. Turn the flour mixture out onto the counter and cut in the butter using a pastry blender or a bench scraper until most of the butter is the size of small peas (you will have some larger and smaller chunks – this is not only OK, but desirable).
4. Make a well in the center of the flour mixture and add half of the water. Gently stir the flour into the water. As the flour becomes moistened and forms walnut-sized clumps, remove them from the mixture and incorporate flour from the outside of the pile. Add the remainder of the water and continue to mix, gently, until all the flour is moistened. If additional water is needed, add it slowly, one half-teaspoon at a time. When the dough is adequately hydrated, it will still appear dry to the touch, but there should be no streaks of visibly dry flour.
5. Gather the dough into a pile. It will appear very shaggy at this point. Using the palm of your hand, press the dough down and away from you to further combine the ingredients. (Do not knead the dough; rather, simply press it.) Return the pieces of dough to the pile and continue pressing the dough 5 or 6 times until it forms a more cohesive mass, being careful not to overwork the dough.
6. Form the dough into a disc about 1 inch tall and wrap tightly in plastic. Refrigerate the dough for at least 45 minutes or up to 5 days. During this time the water will fully hydrate the flour, the gluten will relax, and the butter will have a chance to re-solidify.
7. Roll the dough out into a circle large enough to fit your tart ring. (If it's been refrigerated for longer than an hour and has become very hard, whack the dough a few times with your rolling pin to temper the butter before attempting to roll it out. This will help prevent cracking.) Trim the dough to the top of the tart ring and prick the bottom all over with a fork. Return to the refrigerator for at least 30 minutes to harden before filling.

1. Filling
2. In a small saucepan, bring the milk, vanilla, and half the sugar to just a boil, stirring periodically to ensure the milk doesn't burn on the bottom of the pan.
3. Meanwhile, combine the remaining sugar, salt, cornstarch, and egg in a medium-sized heatproof bowl, and whisk vigorously.
4. When the milk has just reached a boil, slowly pour it into the egg mixture while whisking constantly to prevent the eggs from scrambling.
5. Return the mixture to the saucepan and bring to a boil, stirring constantly with a wooden spoon for 2 minutes.
6. Pour the custard into a heatproof bowl and stir until the steam has dissipated. Then cover directly with plastic wrap to prevent a skin from forming and cool to room temperature.
7. Stir in the soften butter until well incorporated, then fold in the blackberries. If the berries have very tough centers, remove them. They will break down as they are folded into the custard, but this will only help to color and flavor the whole batch.
8. Spread the custard into the chilled tart shell. If desired, cover directly with plastic and return to the refrigerator to set the custard (this will make it easer to arrange the peaches). Slice the peaches into 1/4" slices and fan on top of the custard. Sprinkle granulated sugar on top of the peaches.
9. Bake the tart at 350 degrees Fahrenheit for 50 minutes to one hour, until the crust begins to turn golden brown and the peaches have baked down. Transfer to a wire rack to cool.