Combine the milk, yeast, and sugar in the bowl of a stand mixer and let it sit for 5 minutes until bubbly. Add the rest of the dough ingredients, except for the butter. Once mostly incorporated, start adding in the butter 1 tablespoon at a time, only adding in the next tablespoon after the first one has been fully mixed in. Knead the dough on medium speed until smooth, shiny, and elastic - about 8-12 minutes.
Spread the dough evenly across the bottom of a 9x13" (23x33cm) well-greased cake pan. Cover with plastic wrap and let it rise until doubled, about 20-40 minutes depending on the temperature in your kitchen.
Preheat the oven to 200℃ / 400℉.
Gently heat the topping ingredients in a small saucepan on the stove until melted and shiny.
With greased fingers, make dimples across the top of the risen dough. Pour the topping evenly over it.
Bake for 20-25 minutes, until golden and bubbly. Let the cake topping harden before slicing into it. This is best served slightly warm on the day it is made.
