Gather all ingredients.
Remove and discard rind from Brie cheese. Place cheese in the freezer for 20 minutes to make it easier to cut.
Meanwhile, oil a 24-cup mini muffin pan with cooking spray.
Roll puff pastry sheet out into a 10x14-inch rectangle. Cut sheet lengthwise into 4 even strips and then crosswise into 6 even strips, making 24 squares. Separate squares and gently press each one into a prepared muffin cup.
Remove chilled Brie from the freezer; cut into 24 pieces, approximately ¾-inch in size.
Add 1 teaspoon cranberry sauce to each pastry-lined muffin cup, then press in a piece of Brie and top with 1 teaspoon chopped walnuts. Season each bite with a pinch of sea salt. Transfer muffin pan to the refrigerator and chill for at least 30 minutes, or cover and chill for up to 3 days. When ready to bake, preheat the oven to 400 degrees F (200 degrees C).
Bake bites in the preheated oven until golden brown, 18 to 20 minutes.
Serve warm, and enjoy!
