Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.

In a large bowl, cream together the butter (ing_9) and granulated sugar (ing_7) until light and fluffy.

Beat in the eggs (ing_1) one at a time, then stir in the vanilla (ing_14).

In a separate bowl, whisk together the flour (ing_3), baking powder (ing_5), cornstarch (ing_6), and salt (ing_8).

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Stir in the strawberry preserves (ing_2).

Roll dough into 1-inch balls and place them on the prepared baking sheets. Bake for 10-12 minutes, or until edges are lightly golden.

While cookies are still warm, whisk together the powdered sugar (ing_12) and a little milk (ing_10 or ing_11) to make a glaze. Drizzle over the cookies.

Immediately sprinkle with sanding sugar or sprinkles (ing_13) before the glaze sets.