Strawberry Pop-Tart Cookies

Directions

1. In a small saucepan, warm the jam to a low simmer. In a small bowl, whisk together cornstarch and water. Add to the jam; cook for 3-4 minutes, stirring occasionally, until the mixture loses its cloudy appearance. Transfer to a bowl to cool.
2. Meanwhile, in the bowl of a stand mixer fitted with a paddle attachment, cream butter and the sugar until light and fluffy, 3-5 minutes. Add egg and egg yolk, beating well until incorporated. Beat in sour cream and vanilla.
3. In a separate large mixing bowl, whisk together flour, cornstarch, baking powder, baking soda and salt. With the mixer on low, gradually add dry ingredients, mixing just until no dry patches remain, taking care not to overmix.
4. Cover; chill at least 1 hour or overnight. Meanwhile, transfer the cooled jam mixture to a piping bag fitted with a small, round tip. Chill until ready to use.
5. Divide dough into 2 tablespoonfuls. One at a time, flatten a ball of dough into a 3-in. disc; shape into a shallow bowl. Pipe 1-2 teaspoons of jam into the center, then bring up the edges of the dough to completely encase the jam; pinch to seal. Repeat with the remaining balls of dough. Arrange, seam side down, on two 15x10x1-in. parchment-lined baking sheets, spacing at least 2 in. apart. Refrigerate at least 15 minutes.
6. Preheat the oven to 350°. Bake 10-12 minutes or until the centers appear set and the edges are lightly golden. Remove promptly; let cool on the baking sheet for 10 minutes.
7. Meanwhile, in a small bowl, whisk together confectioners' sugar and milk until smooth. Spoon 2 teaspoons of icing onto each cookie, using the back of a spoon or an offset spatula to spread it into an even layer. Immediately sprinkle with a generous pinch of rainbow sanding sugar. Let set 10 minutes.