Slice the 10 tablespoons unsalted butter into pieces and melt it in a light-colored skillet over medium whisking constantly. Once melted, the butter will begin to foam. Continue whisking for about 5-7 minutes, the butter will become a deep amber color. Remove the browned butter from the heat, and pour it into a bowl. Cover and refrigerate until firm. This should take about four hours but I often brown the butter the night before.
Add the 3 cups all-purpose flour, ½ cup brown sugar, 1 tablespoon baking powder, 2 teaspoons cinnamon, 1 teaspoon kosher salt, and ½ teaspoon baking soda to the bowl of your food processor.
Cut the chilled brown butter into 4 pieces and added it to the food processor. Pulse a few times to chop and incorporate the butter into the dry ingredients. Continue processing until the butter pieces are the size of peas. Stir in the ½ cup finely chopped pecans.
In a large bowl whisk together the 1 cup heavy whipping cream, 1 large egg, and 1 teaspoon vanilla extract.
Pour the wet ingredients into the dry ingredients and fold them together being careful to not over mix.
Pour the dough onto a lightly floured counter. Knead the dough a few times until it begins to come together and smoothes out a bit. Flatten the dough and fold it into thirds like you would a letter. Give the dough a quarter turn and repeat this flattening and folding process two more times.
Pat the dough into a rectangle approximately 1 inch thick and cut into one-inch squares using a sharp knife.
Transfer the dough squares to a parchment paper-lined baking sheet and refrigerate while you make the pumpkin custard.