Preheat the oven to 200-220 degrees top / bottom heat.
Let the frozen puff pastry thaw well and roll out the sheets. Cut each plate into 2 triangles with 2 long sides. Mix all ingredients for the filling together and place 1 tablespoon of the filling on each triangle.
Cut into the short side of the triangle and loosely roll the triangles into croissants. Place on a baking sheet lined with baking paper and brush with the beaten egg yolk.
Let rest for 15 minutes and then bake on the middle rack for 15-20 minutes. The baking time varies depending on the oven and the desired degree of browning.