Preheat your oven to 200°C (400°F) and line a baking tray with parchment paper. While the oven heats, whisk together the room temperature egg yolk with milk in a small bowl until fully combined—this creates a glossy, even coating on the pastry. I always make sure the egg yolk is at room temperature because it whisks more smoothly and distributes evenly, giving you a beautiful golden sheen.

Remove the puff pastry sheets from the freezer and let them sit at room temperature for 2-3 minutes to soften slightly—this makes them easier to cut without cracking. Unroll the pastry and cut it into triangles (typically you'll get 8 triangles per sheet). Place about 1 teaspoon of jam on the wider base of each triangle, then roll tightly from the base toward the point. Gently bend the rolled pastry into a crescent shape and place on the prepared tray, spacing them about 2 inches apart.

Using a pastry brush, apply the egg wash mixture from Step 1 evenly over the top of each croissant—this gives them that signature golden, shiny finish. Bake for 17-20 minutes until the pastry is puffed and deeply golden brown. I watch them closely toward the end of baking because puff pastry can brown quickly, and you want a beautiful color without burning.

Remove the croissants from the oven and transfer them to a cooling rack—this allows air to circulate underneath and keeps the bottoms crispy. Let them cool for 3-5 minutes until they're warm but not hot. Dust the tops generously with sifted icing sugar, which gives a beautiful, even coating without lumps.