Make the Focaccia Bread: In a stand mixer with a dough hook, combine the warm water, yeast, sugar, salt, and flour. Then, on a medium to low speed, knead the bread for 4 minutes until it's fully combined. Dough should be smooth and elastic. If needed, add a couple of tablespoons of flour at a time until the bread dough is no longer sticky.
Make the Cinnamon Sugar Sauce: In a medium to large saucepan, melt the 3/4 cups of butter. Once melted, add the brown sugar, ground cinnamon, and vanilla extract. Stir the sauce occasionally until it is all combined. Then remove it from the heat.
Construct the Focaccia Bread: Grease the large sheet pan with the melted butter. *We line the baking sheet with parchment paper and then grease the paper. This allows for easy cutting of the bread while still getting crisp buttery edges.
After the pan is greased, turn out the dough onto the sheet pan and carefully stretch it to fit with your hands. Then, spoon half the cinnamon sugar onto the bread dough, spreading it evenly over the entire surface.
Fold the dough in a letter fold, bringing the top halfway down to the center, and then bring the bottom half up and over the center to meet the top edge.
Cover the prepared dough with plastic wrap and let it rise for 45 minutes.
Bake the Cinnamon Focaccia Bread: When it is 30 minutes into the rise time, preheat the oven to 400°F.
Remove the plastic wrap, then dimple the bread by pressing your fingers firmly all over, stretching it back out to the size of the sheet pan. Pour the remaining cinnamon sugar over the bread, then bake for 20 minutes, or until the edges are golden brown.
Once baked, remove the bread from the oven and let it cool for 5-10 minutes.
While the bread is cooling, prepare the glaze. In a small mixing bowl, whisk the powdered sugar, vanilla, and milk with a fork, then add 1 tbsp of milk at a time until you reach the desired consistency.
Drizzle the glaze over the slightly warm bread. Then cut the bread, serve it warm, and enjoy!