Heat the oven to 375°F (190°C) and line a baking sheet with parchment paper. Beat the softened cream cheese, granulated sugar, vanilla, and lemon zest until smooth.

If using flour, gently toss it with the blueberries. Separate the crescent dough into eight pieces and flatten each one into a small circle, keeping the center slightly thicker than the edges.

Place about 1 tablespoon of cream-cheese filling and 1–2 teaspoons of blueberries in the center of each dough circle. Fold the dough up and around the filling, pinching all seams firmly closed.

Arrange the filled dough seam-side down on the prepared baking sheet. Refrigerate for 10–15 minutes if the dough has become soft or difficult to handle.

Brush the tops with melted butter and sprinkle with graham-cracker crumbs if desired. Bake for 16–20 minutes, until puffed and golden brown.

Cool the baked bombs for at least 10 minutes because the filling will be very hot. Whisk the powdered sugar with enough milk or lemon juice to create a thick drizzle, then spoon it over the cooled pastries.