Dissolve yeast in warm milk and water in a small bowl. Add a pinch of sugar if desired. Let it sit for 5 minutes until foamy.

In the bowl of a stand mixer fitted with the paddle attachment, cream butter, sugar, and salt until combined.

Beat in the egg until incorporated.

With the mixer on low speed, slowly add the flour, then pour in the yeast mixture.

Mix on medium-high for 2–3 minutes until the dough is smooth and pulls away from the sides of the bowl.

Spread the dough into a greased 9x13-inch baking pan, pressing evenly to the edges and corners with your hands or an offset spatula.

Cover with a clean kitchen towel and let rise until doubled in size, about 1½–2 hours with active dry yeast or 1 hour with instant yeast.

Preheat the oven to 375°F.

In a small bowl, whisk together corn syrup, water, and vanilla. Set aside.

In the stand mixer with the paddle attachment, cream butter and sugar on medium speed until a thick paste forms.

Beat in the egg until incorporated and lightened.

Reduce mixer speed to low and slowly add flour and salt until combined. The mixture will resemble thick sugar cookie dough.

Add the corn syrup mixture, then increase the speed to medium-high and beat until smooth.

Dollop the topping evenly over the risen dough.

Spread gently with a small offset spatula or the back of a spoon to cover the surface.

Bake for 30–35 minutes, rotating the pan after 20 minutes, until golden brown. The edges will be darker and the center puffed but cohesive, similar to cheesecake.

Cool slightly on a wire cooling rack, then dust with confectioners' sugar using a fine-mesh sieve before serving.