01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat the softened butter and granulated sugar with an electric mixer on medium speed until pale, light, and fluffy, approximately 3 minutes.
04 - Beat in the egg and vanilla extract until the mixture is smooth and fully incorporated.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until a soft, cohesive dough forms. Do not overmix.
06 - Scoop 2-tablespoon portions of dough and roll into balls. Flatten each ball slightly in your palm. Spoon 1/2 teaspoon of strawberry jam into the center of half the dough rounds. Place a second dough round on top of each jam-topped piece, pinch the edges firmly to seal, and gently flatten to enclose the filling.
07 - Place the filled cookie shells on the prepared baking sheets, spacing them about 2 inches apart to allow for spreading.
08 - Bake for 12 to 13 minutes, or until the edges are just turning golden. Allow the cookies to rest on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely.
09 - In a small bowl, whisk together the powdered sugar, 1 tablespoon of milk, and vanilla extract until smooth. Add additional milk as needed, a small splash at a time, until the glaze is thick yet pourable.
10 - Drizzle or spread the glaze over the fully cooled cookies. Immediately sprinkle with crushed freeze-dried strawberries or colorful sprinkles before the glaze sets.