1. Preheat the oven to 350°F (175°C) and lightly grease a standard 12-cup muffin tin.

2. Unroll the refrigerated pie crusts on a lightly floured surface and gently roll them out to even the thickness.

3. Use a round cutter slightly larger than the muffin cups to cut circles from the dough, re-rolling scraps as needed.

4. Press each dough circle into the prepared muffin cups, making sure the dough comes up the sides to form small tart shells.

5. Place the muffin tin in the refrigerator to chill while you prepare the filling.

6. Add the unsalted butter to a light-colored saucepan and set over medium heat.

7. Melt the butter, then continue cooking, swirling the pan often, until it foams and the milk solids turn golden brown and smell nutty.

8. Remove the pan from the heat immediately and pour the browned butter into a heatproof bowl to cool slightly.

9. In a medium mixing bowl, whisk together the pure maple syrup and packed light brown sugar until the sugar starts to dissolve.

10. Slowly whisk the slightly cooled brown butter into the maple mixture until combined.

11. Add the large eggs and egg yolk to the bowl and whisk until the mixture looks smooth and glossy.

12. Whisk in the vanilla extract, fine sea salt, and heavy cream until everything is evenly blended.

13. Stir in the finely chopped pecans until they are evenly distributed in the filling.

14. Remove the chilled tart shells from the refrigerator and place the muffin tin on a baking sheet for easy handling.

15. Divide the maple brown butter filling evenly among the tart shells, filling each one about two-thirds full.

16. Sprinkle the tops with the roughly chopped pecans if using.

17. Transfer the muffin tin to the oven and bake for 18 to 22 minutes, or until the crusts are golden and the centers are puffed with just a slight wobble in the middle.

18. Remove the tartlets from the oven and let them cool in the pan for 10 minutes.

19. Carefully loosen the edges with a small knife or offset spatula and transfer the tartlets to a wire rack to cool completely or until just warm.

20. Finish with a light pinch of flaky sea salt on each tartlet before serving, if desired.