Preheat the oven to 400ºF. Spray a mini muffin tin generously with cooking spray.
Prepare the puff pastry: Dust your countertop and a rolling pin with flour. Place the puff pastry sheet on the cutting board and roll it into an approximate 10-inch x 15-inch rectangle. Use a large knife to cut the puff pastry into 24 (2.5-inch) squares (4 columns by 6 rows). Place each square into the mini muffin tin, and use your fingers to press the pastry into the sides of the tin to create a cup. Use a fork to prick the bottom of each cup 2 times; this will help prevent the cup from puffing up too much!
Fill the puff pastry bites: Dollop about ½ to ¾ teaspoon of fig jam into each puff pastry cup. Add a few crumbles of goat cheese and about 1 teaspoon of chopped walnuts to each cup.
Brush with egg wash: In a small bowl, mix together the egg with a fork and use a pastry brush to brush on the edges of the puff pastry crust. This will help to create a nice golden brown crust when baked.
Bake the bites: Bake for 12-14 minutes until the puff pastry is golden brown and the cheese is nice and melty.
Finish and serve: Remove the pan from the oven and sprinkle a tiny bit of the finely chopped rosemary and a pinch of flaky sea salt onto each bite. Let cool for 5 minutes, then use a fork to remove each bite from the muffin tin. Makes 24 bites. Enjoy!
