9tablespoons(4 ½ ounces) unsalted butter, cold and cut into small cubes
1extra-large egg
For the Filling
1poundlight brown sugar
4extra-large eggswhole or 2%
¼cupmilk
2teaspoonspure vanilla extract
¼teaspoonKosher salt
Pinchof ground cinnamonoptional
6ouncesunsalted buttermelted and lightly browned
Accompaniment
Lightly sweetened whipped cream
Instructions
For the Tart Dough
In the bowl of a food processor, add the flour, sugar, and salt. Pulse until combined. Scatter the butter pieces over the flour. Process in short bursts until the butter is the size of peas. Add the egg and process in long pulses (about 5-7 seconds long) until the dough has started to clump. Place a piece of plastic wrap on the counter and dump the dough onto the surface. Using the plastic wrap and the back of your hands, gently press the dough into a disk. Wrap tightly with the plastic wrap and refrigerate for at least 2 hours, preferably overnight.
Preheat the oven to 325℉.
Remove the dough from the refrigerator. If refrigerated overnight, let it rest at room temperature for 10 minutes. On a lightly floured work surface, roll the dough out into a 12-inch circle, flouring the dough and surface as necessary to keep the dough from sticking. Roll up the dough around the rolling pin and gently unroll it over a 9 ½-inch tart pan with a removable bottom. Fit the dough into the edge of the pan. Roll the rolling pin over the top of the pan to remove the excess dough; set in the refrigerator until ready to use.
For the Filling
In a medium bowl, whisk together the brown sugar, eggs, milk, vanilla, salt, and cinnamon (if using) until smooth. In a slow, steady stream, add the browned butter, whisking constantly.
Pour the filling into the tart shell. Set the tart shell on a rimmed baking sheet and bake for 50-60 minutes or until puffed and golden.
Transfer the tart to a wire rack and cool to room temperature before cutting. The filling will fall slightly, and the top will become firm like a meringue. Serve as is or top with lightly sweetened whipped cream. Leftovers can be wrapped with plastic wrap and stored at room temperature for up to 2 days. Enjoy!
Notes
Lightly browning the butter gives the filling a rich and nutty flavor.