I love desserts that are rustic and warm, which is why I love to make these free-form tarts. I replace milk, cream, and water with butter so that once they're baked, they spread out and take on a shape of their own. The unsweetened cream on top, paired with the sweetness of the tart, creates a perfect balance for the palate.
Dough: Combine the flour, sugar, and butter in the bowl of a standing mixer fitted with a paddle attachment and mix on low speed until the butter and dry ingredients form a coarse cornmeal consistency, about 2 minutes. Add the vanilla and mix on medium speed until the dough is smooth, 2–3 minutes. Dust a flat work surface with flour and turn the dough out onto it. Knead the dough for a few minutes until it comes together. Bring the dough into a ball, wrap it tightly with plastic wrap, and chill for at least 1 hour and up to 3 days. (The dough can also be frozen for 2 months; when you're ready to use it, defrost overnight in the refrigerator.)
Remove the dough from the refrigerator. Dust a flat work surface with flour, cut the dough into chunks, and pound with a rolling pin on the countertop to soften until it is the texture of Play-Doh. Then knead it to make it pliable. Do not overwork the dough. Lightly dust the rolling pin with flour and roll the dough out to an even ¼-inch thickness. With a 5-inch cookie cutter, cut circles from the dough as close together as possible. Carefully place the circles of dough on a lined baking sheet, flouring each one to prevent sticking, and chill. (You can only re-roll the dough once. Discard the remaining scraps.)
Apple filling: Put apples in a large mixing bowl. Make the vanilla brown butter: Split and scrape the vanilla pod and combine both pod and its seeds with the butter in a small saucepan over high heat. Swirl as the butter becomes foamy. Pour the browned butter over the apples and stir to coat. Add the granulated sugar, brown sugar, and cinnamon, and stir to combine. Set aside for 30 minutes to bring out the juices in the apples. Stir in the cornstarch, then the crème fraîche.
Streusel topping: Combine flour and sugar in a medium bowl and toss in the butter. Using your fingertips, break up the butter in the flour to make pea-size lumps.
Preheat oven to 375 degrees F. To assemble the tarts, warm the discs of dough between your fingertips so that they are pliable enough to fold. Spoon 1 tablespoon of applesauce and ¼ cup apple filling into the center of each disc. Pleat the dough to seal, and transfer each tart onto a lined baking sheet, spaced about 2 inches apart. Sprinkle 2 tablespoons of streusel topping onto each tart. Bake the tarts until golden-brown, rotating the baking sheets halfway through, about 30 minutes. Let them cool while you make the whipped cream.
Whipped cream: Pour cream into the chilled bowl of an electric mixer fitted with a whisk attachment, and mix on medium until soft peaks form. Add the crème fraîche and beat on medium until mixture is thick and mousse-like. Add more crème fraîche to make it softer and shinier, if you like. Dollop onto the apple tarts, and serve.