Preheat the oven to 375°F. Lay out the puff pastry sheet flat on a baking sheet. Trim the edges so they are round and you have an oval shape. Save the extra pieces of puff pastry dough.
Melt the butter and using a brush, brush the melted butter inside the puff pastry. Place the brie in the center of the puff pastry dough.Spread the jam on top of the brie.
Bring the edges of the puff pastry dough up over the top and seal well, using most of the remaining butter.
Using a cookie cutter and the extra pieces of puff pastry dough cut out a few hearts. Place the heart cutouts on top.
Brush the top well with the rest of the butter.Bake in a preheated 375°F oven for 20 minutes. Remove and let sit for at least 20 minutes before serving.