01 - Preheat 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.
03 - In a large bowl, beat the softened unsalted butter, granulated sugar, and light brown sugar using an electric mixer until the mixture is light and creamy, about 2 to 3 minutes.
04 - Add the large egg and vanilla extract to the creamed butter mixture. Beat until fully combined and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed just until the dough comes together. Avoid overmixing.
06 - Scoop 1 tablespoon of dough and flatten it slightly in the palm of your hand. Place 1/2 teaspoon of strawberry jam in the center, then cover with another tablespoon of dough. Pinch the edges together to seal completely and gently roll into a smooth ball. Repeat with the remaining dough and jam.
07 - Place the filled cookie dough balls onto the prepared baking sheets, spacing them approximately 2 inches apart to allow for spreading.
08 - Bake for 12 minutes, or until the edges are lightly golden. Allow the cookies to rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
09 - In a small bowl, whisk together the powdered sugar, milk, vanilla extract, and a drop of food coloring if desired, until the glaze is smooth and slightly thickened. Spread the glaze over the fully cooled cookies and decorate with rainbow sprinkles. Allow the glaze to set before serving.