Mix the butter with the powdered sugar, then add the egg yolk and mix until smooth and buttery.

Add flour and a pinch of salt, and knead just until you have a smooth butter cookie dough.

Fill the cookie dough into a decorating bag attached with a decorating tip. (I use 2 decorating piping tips in this recipe: the open star tip and the star tip)

Pipe the cookie in a small rose shape onto a baking sheet covered with parchment paper. With a wooden spoon, make a small hole in the middle of the cookies for the filling.

Bake in preheated oven for 12 minutes at 180°C (365°F) or until the cookies are light golden.

Fill cookies with strawberry jam (watch the above video for more instructions).

Store in cookies jar at room temperature.