In a large mixing bowl, whisk together the all-purpose flour, salt, and granulated sugar.

Add the chilled, cubed butter to the dry mixture and mix until it resembles coarse crumbs.

Gradually add cold water, one tablespoon at a time, until the dough comes together. Divide into two discs, wrap in plastic wrap, and refrigerate for at least 30 minutes.

While the dough chills, prepare the filling by mixing the fruit jam or preserves with 1/4 teaspoon of vanilla extract.

Preheat your oven to 350°F (175°C). Roll out one disc of dough to 1/8-inch thickness and cut into rectangles (3x4 inches).

Place half of the rectangles on a baking sheet lined with parchment paper. Spoon about 1 tablespoon of filling onto the center of each rectangle.

Roll out the second disc of dough, cut into rectangles, and place over the filled rectangles. Press edges to seal and crimp with a fork.

Bake in the preheated oven for 20-25 minutes or until golden brown. Let cool on a wire rack.

Prepare the icing by mixing powdered sugar, milk, and 1/2 teaspoon of vanilla extract until smooth. Drizzle over cooled Pop Tarts.