Thaw the puff pastry at room temperature and then unfold it. Preheat the oven to 400 F. Cut the pastry into an even number of pieces of whatever size you want. I cut mine into thirds length-wise (as it was folded), then cut each third into six pieces I think. Line a cookie sheet with parchment paper and place all the pastry pieces on it. Bake for 10 minutes. Remove and let cool completely.

Whisk the mascarpone cheese with the sugar and lemon juice.

Whip the cream.

Split the pastry pieces in half and spread mascarpone on one piece. Top it with another piece of pastry, spread whipped cream on that, then top with raspberries.

Refrigerate until serving.