In a mixing bowl, combine gluten-free flour and sugar. Add cold butter and mix until crumbly.

Gradually add cold water until the dough comes together. Wrap in plastic wrap and refrigerate for 30 minutes.

In a saucepan, combine strawberries, sugar, cornstarch, and lemon juice. Cook over medium heat until thickened, about 5-7 minutes.

Preheat the oven to 350°F (175°C). Roll out the dough on a floured surface to about 1/8 inch thickness.

Cut into rectangles and place half on a baking sheet lined with parchment paper. Spoon filling onto each rectangle.

Top with remaining rectangles and seal edges with a fork. Brush with egg wash.

Bake for 20-25 minutes or until golden brown. Let cool.

In a bowl, whisk together powdered sugar, milk, and vanilla until smooth. Drizzle over cooled poptarts.