Using a rubber spatula mix the egg, brown sugar, softened butter, vanilla extract, and salt until well combined. Stir in the pecans. Spoon the filling evenly into each mini muffin tin on top of the chocolate layer.
1 large egg, ¾ cup packed brown sugar, 1 tablespoon unsalted butter, softened, 1 teaspoon pure vanilla extract, ⅛ teaspoon salt, ⅔ cup finely chopped pecans