In a small bowl, combine warm water with sugar. Sprinkle yeast on top and let it sit for 10-15 minutes until foamy.

In a large mixing bowl, whisk together bread flour and salt. Add the activated yeast mixture and olive oil, stirring to form a sticky dough.

Cover the bowl and refrigerate for at least 12 hours for the first rise.

Preheat your oven to 450°F. Grease a baking pan with olive oil. Gently deflate the chilled dough and add melted butter before transferring it to the pan. Cover and let it rise for 1.5 to 2 hours.

In a saucepan, melt unsalted butter until golden brown and nutty, about 5-7 minutes. Allow to cool slightly.

Combine light brown sugar and cinnamon with the cooled brown butter in a small bowl.

Make dimples in the risen dough and drizzle the topping evenly over it.

Bake for 20-25 minutes until golden brown.

While cooling, prepare the icing by mixing powdered sugar, milk, and vanilla extract until smooth. Drizzle over the focaccia.