Cut the butter into small pieces and leave it at room temperature until softened. The butter should be soft enough that a gentle press with your finger leaves an impression. Properly softened butter ensures it mixes smoothly with other ingredients, resulting in crisp cookies.

In a mixing bowl, combine the softened butter and 20g powdered sugar. Gently mix with a spatula until the sugar and butter are well combined, being careful not to overmix.

Add the egg yolk and use an electric mixer to blend until fully incorporated. Make sure the yolk is at room temperature to prevent the mixture from separating. Stir until smooth and creamy.

Sift the 145g cake flour into the bowl, and gently fold the mixture using a spatula. Use a "Z" motion or fold from the bottom up to avoid overmixing, which could make the cookies tough. Stop mixing as soon as the dough comes together.

Use your hand to knead the dough in the bowl until it comes together smoothly. Then transfer it to a chopping board and continue kneading lightly by hand until the dough is smooth and uniform, about 1-2 minutes.

Divide the dough into 20 equal portions (about 14g each). Use a kitchen scale for consistency.

Roll each portion into a ball, place it on a baking sheet lined with parchment paper, and press it gently into a flat circle about 0.5–1cm thick.

Shape each circle into a heart with your fingers or a small tool.

Pipe or spoon a small amount of strawberry jam into the center of each cookie. Adjust with a small spoon to ensure it's neatly placed.

Place the shaped cookies into the freezer for 10 minutes to firm up. This helps them maintain their shape during baking.

Preheat your oven to 160°C (320°F). Bake the cookies on the middle rack for about 20 minutes.

Watch closely as the cookies bake. They are ready when the edges turn a light golden brown.

Remove the cookies from the oven and transfer them to a cooling rack. If desired, sprinkle shredded coconut over the cookies while they are still warm.