Preheat the oven to 350°F. Lightly grease an 8-inch skillet or line with parchment paper.

In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light, fluffy, and smooth.

Add the egg, egg yolk, vanilla extract, and almond extract. Mix until fully combined and glossy.

In a separate bowl, whisk together the flour, cornstarch, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Fold in the rainbow sprinkles and white chocolate chips, if using.

Press the dough evenly into the prepared skillet.

Bake for 18–22 minutes, or until the edges are lightly golden and the center looks slightly underbaked.

Let cool for 10–15 minutes before scooping. Serve warm for the ultimate gooey texture.