• Preheat oven to 400° and spray a mini muffin tin with nonstick spray. Set aside.

Prepare the Apple Filling:

• Melt butter in a large skillet over medium heat. Once melted, add the diced apples, maple syrup, cinnamon, and vanilla. Stir to evenly coat the apples. Sauté, stirring occasionally, for 7-10 minutes, or until apples have cooked down and are tender.
  4 apples, 2 tablespoons butter, 2 tablespoons maple syrup, 1.5 teaspoons cinnamon, 1 teaspoon vanilla

Prepare the Crumb Topping:

• Using a pastry cutter, cut the cold butter until it's in small, pea-sized pieces.
  1/4 cup butter
• Add flour, sugar, brown sugar, and cinnamon, and stir to incorporate. The mixture will look a little dry and very crumbly.
  1/4 cup all-purpose flour, 2 tablespoons sugar, 2 tablespoons light brown sugar, 1/4 teaspoon cinnamon

Assemble Apple Crumble Tarts:

• Cut the sheet of puff pastry into 24 evenly-sized pieces. Using your hands, gently stretch and pull each puff pastry rectangle into more of a square.
  1 sheet puff pastry
• Place a puff pastry square into each prepared mini muffin tin cavity, lightly pressing it against the bottom and sides.
• Fill with the apple filling, then top generously with the crumble topping.
• Place into the oven and bake for 12-15 minutes, or until the pastry is golden brown.
• Remove from oven and let cool at least 5 minutes in the muffin tin. If desired, sprinkle with powdered sugar before serving.