Preheat the oven to 400ºF.
Cook the bacon in a large saucepan over medium heat until a majority of the fat has rendered. Using a slotted spoon, transfer the cooked bacon to a paper towel-lined plate.
In the bowl of a stand mixer fitted with the paddle attachment, cream together 12 tablespoons (1 1/2 sticks) butter with 1/3 cup light brown sugar until light and fluffy, about 2 minutes.
Divide the butter mixture between the cups of a nonstick 12-cup muffin pan. Divide the chopped pecans and cooked bacon between the cups, sprinkling them on top of the butter. (See Notes.)
Lightly flour your work surface. Unfold one sheet of puff pastry onto the surface with the folds opening left to right.
Brush the whole sheet of pastry with half of the melted butter then sprinkle it with half of the light brown sugar and half of the cinnamon. Starting at the bottom edge (closest to you), tightly roll up the pastry ending with the seam side down. Trim and discard the two ends then cut the roll into 6 equal pieces, about 1 1/2 inches wide. Place each piece, spiral facing up, in each of six muffin cups. Repeat the filling, rolling and slicing process with the second sheet of puff pastry to make 12 sticky buns.
Place the muffin pan on a baking sheet lined with parchment paper (to catch any overflow) and bake the sticky buns on the center rack for 25 to 30 minutes until the buns are golden brown and firm to the touch. Remove the sticky buns from the oven and allow them to cool in the pan for 5 minutes only.
then invert the pan onto the parchment paper-lined baking sheet, scraping out any topping from the cups. Let the buns cool slightly then serve.
It's important that you sprinkle the chopped pecans and bacon on top of the butter mixture in each muffin pan so that they do not burn while baking.
Do not let the sticky buns cool for longer than 5 minutes in the pan or the topping will become too hard and not release along with the buns when you invert the muffin pan onto the baking sheet.