Place the brie cheese in the freezer for 15 minutes. Preheat the oven to 375 degrees Fahrenheit.
Lay out the puff pastry on a floured surface and use a rolling pin to roll it into a 10”x14” rectangle. Then use a knife to cut it into four strips one way and 6 strips the opposite way, making 24 equal squares.
Remove the brie cheese from the freezer and cut it into 24 squares.
Spray a mini muffin tin with nonstick spray. Then place each square of puff pastry in a mini muffin tin, pressing it down slightly. Use a fork to poke the bottom of each puff pastry square 3 times.
Add a square of brie into each muffin tin. Then add ½ tsp of raspberry jam and ½ tsp of chopped walnuts.
Remove the leaves from the sprig of rosemary and chop the herb finely. Add a pinch of rosemary leaves and a pinch of flakey sea salt into each muffin tin.
Place the muffin tin on a cookie sheet and bake in the oven for 20-22 minutes.
Allow the brie cheese bites to cool slightly before serving. Serve and enjoy!