Preheat the oven to 425°F / 218°C. Thaw frozen puff pastry per packaging instructions and roll out slightly.

Cut each puff pastry sheet into 4 equal squares for a total of 8 squares.

Brush each square with egg wash, fold into triangles, and seal edges. Brush tops with egg wash and sprinkle with coarse sugar.

Bake for 22-25 minutes until deep golden brown. Cool completely.

In a pot over medium heat, combine frozen blueberries, blackberries, raspberries, sugar, and lemon juice. Cook for 15-20 minutes until thickened. Set aside to cool.

In a mixing bowl, beat heavy cream, powdered sugar, and vanilla extract until stiff peaks form. In another bowl, beat cream cheese and sour cream until fluffy. Fold whipped cream into the cream cheese mixture.

Slice each croissant in half, spread jam on both sides, fill with cream filling, and dust with powdered sugar. Serve immediately.