01 - Preheat 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 light and fluffy, approximately 3 minutes.
04 - Add the egg and vanilla extract to the butter mixture, beating until fully combined and smooth.
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 onto the center of half the dough rounds. Top each filled round with another flattened dough piece, pinch the edges firmly to seal, and gently press to enclose the jam inside.
07 - Place the sealed 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 cookies to rest on the baking sheet for 5 minutes, then transfer to a wire cooling rack to cool completely.
09 - In a small bowl, whisk together the powdered sugar, 1 tablespoon of milk, and vanilla extract until smooth and thick but still pourable. Add additional milk as needed to reach desired consistency.
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.