Activate the Yeast:
In a small bowl, combine warm water (about 110°F) and granulated sugar. Sprinkle the active dry yeast over the top and let it sit for 10-15 minutes until it becomes foamy.

Mix the Dough:
In a large mixing bowl, whisk together the flour and salt. Then, pour in the activated yeast mixture along with the olive oil. Stir everything together until the dough forms a sticky ball. Lightly rub the surface of the dough with olive oil.

First Rise:
Cover the bowl with a damp tea towel or plastic wrap. Place it in the refrigerator for at least 12 hours to rise.

Second Rise:
Grease a 9×13-inch baking pan and line it with parchment paper. Pour 2 tablespoons of melted butter into the center of the pan. Gently deflate the dough by pulling it from the sides of the bowl and folding it toward the center. Repeat this process several times. Then, transfer the dough into the buttered pan. Cover and let it rise for 1 ½ to 2 hours in a warm spot.

Make the Brown Butter:
In a small saucepan, melt ½ cup butter over medium heat. Continue stirring until the butter develops a nutty aroma and turns a golden-amber color. Remove from heat immediately to prevent burning. Let it cool for about 10 minutes.

Make the Cinnamon Topping:
Add the brown sugar and cinnamon to the browned butter, mixing until the sugar is dissolved.

Dimple the Dough:
Preheat your oven to 450°F. Once the dough has risen for the second time, use wet fingertips to press deep dimples all over the surface. Then, drizzle the cinnamon-butter evenly over the dimpled dough.

Bake:
Bake for 20-25 minutes, until the focaccia is golden brown. Let it cool for 10 minutes in the pan before transferring to a cooling rack.

Finish with Vanilla Icing:
In a bowl, combine the powdered sugar, milk, and vanilla extract. Mix until smooth. Drizzle the icing evenly over the warm focaccia.

Serve & Enjoy:
Slice into squares and enjoy!