Make the Shortbread Dough:

1. Cream the butter and sugar:
   • In a mixing bowl, beat the softened butter and caster sugar together until light and fluffy. Add the vanilla extract and mix until combined.
2. Add dry ingredients:
   • Gradually sift in the flour and salt, mixing until a soft dough forms.
3. Chill the dough:
   • Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.

Shape and Bake the Cookies:

4. Preheat oven:
   • Preheat your oven to 350°F (180°C). Line a baking sheet with parchment paper.
5. Roll and cut:
   • Roll out the chilled dough to about 1/4 inch thickness on a lightly floured surface. Use a heart-shaped cookie cutter to cut out cookies. For half the cookies, cut a smaller heart in the center to create a “window.”
6. Bake:
   • Place the cookies on the prepared baking sheet and bake for 10–12 minutes, or until the edges are lightly golden. Cool completely on a wire rack.

Assemble the Cookies:

7. Add the filling:
   • Spread a small amount of strawberry jam on the solid cookies. Top with the “window” cookies to create a sandwich.

Make the Strawberry Glaze:

8. Prepare the glaze:
   • In a small bowl, whisk together the strawberry puree, icing sugar, milk, and melted butter until smooth.
9. Decorate:
   • Drizzle or spread the glaze over the top of the cookies. Let the glaze set before serving.