Cut out circles from puff pastry using a round cookie cutter. I cut out 4" circles for my mini galettes.
Pierce the center of the pastry with a fork and use a knife to score an inner edge to the pastry circles to create a crust.
Cut up the butter into small diced cubes. Place one cube in the center of each pastry square along with a pinch of brown sugar.
Place apple slices on top of the butter/brown sugar. Repeat with each galette.
Add another butter cube, pinch of brown sugar, and dash of cinnamon on top of the apples.
Top each galette with crumbled walnuts.
Bake for 20 minutes or until edges are golden brown. Watch carefully as ovens vary.
To make caramel sauce, bring 1 cup brown sugar, 1/2 cup butter, cornstarch, and 1/4 cup milk to a gentle boil in a saucepan over medium heat, stirring often. Allow to cook, boiling, for 1-2 minutes to thicken sauce. Remove from heat and add in vanilla extract. Stir to combine. Drizzle over apple walnut galettes.