Gather the ingredients. Preheat the oven to 425 degrees F (220 degrees C). Line 2 baking sheets with parchment paper.

Unroll pie crusts, place on a lightly floured work surface, and roll slightly with a rolling pin to square the edges. Cut each crust into 8 equal-sized rectangles.

Place about 1 tablespoon strawberry jam in the center of 8 squares. Spread jam out to within 1/4-inch of the edge. Top each with another pastry square and use a fork to crimp together, sealing in jam. Use a knife to trim pastries, if desired. Transfer filled pastries to the prepared baking sheets.

Bake in the preheated oven until edges are lightly golden brown, about 7 minutes. Allow to cool on the baking sheets.

Whisk confectioners' sugar, milk, and vanilla extract in a bowl to make a spreadable frosting. Add water, a few drops at a time, if needed. Spread cooled tarts with frosting and sprinkle with colored sugar.

Serve and enjoy.