01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, and salt until evenly distributed. Set aside.
03 - In a large mixing bowl, beat the softened butter and granulated sugar with an electric mixer on medium speed until pale, light, and fluffy, approximately 3 minutes.
04 - Add the egg and vanilla extract to the butter mixture. Beat until fully combined and smooth, scraping down the sides of the bowl as needed.
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 the palm of your hand. Spoon 1/2 teaspoon of strawberry jam into 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 completely.
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 brown. Allow the cookies to rest on the baking sheets 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 an additional tablespoon of milk if a thinner consistency is desired.
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. Allow the glaze to firm up before serving.