Prep Filling: Begin by beating the softened cream cheese and powdered sugar together until smooth and creamy. Next, drop dollops of this mixture onto parchment paper and top each with a small dollop of strawberry jam. Freeze these for at least 45 minutes until solid.

Mix Wet Ingredients: In a mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until it becomes glossy. Add in the egg, egg yolk, and vanilla extract, beating until the mixture lightens in color and becomes well combined.

Combine Dry Ingredients: Gradually mix in the all-purpose flour, cornstarch, baking powder, baking soda, and kosher salt until there are no dry flour pockets remaining.

Stuff Cookies: Take about 2 tablespoons of dough and flatten them in your hands. Place a frozen cheesecake filling dollop in the center of each and carefully seal the edges. Roll each cookie ball in the extra granulated sugar.

Bake: Preheat your oven to 350°F (175°C). Bake the cookies for about 12-14 minutes, or until the edges look golden and slightly crinkled.

Cool: Allow the cookies to rest on the baking sheet for 10 minutes before transferring them to a wire rack.