In a small bowl, combine the active dry yeast with half of the warm water and let it sit for about 5-10 minutes until foamy. In a larger bowl, whisk together the unsalted butter, sugar, kosher salt, and the remaining warm water. Stir in the egg yolk and the yeast mixture before gradually incorporating the all-purpose flour until a soft dough forms.

Lightly grease a 9x13 baking dish with melted butter and spread the dough evenly across the bottom, pressing gently to fit. Cover the pan with a clean kitchen towel and allow the dough to rest for 15 minutes.

Preheat your oven to 350°F (175°C). Gather your toppings, including shredded mozzarella and grated Parmesan cheese.

Uncover the dough and brush the top with melted butter. Sprinkle generously with mozzarella cheese, followed by Parmesan, garlic salt, and dried oregano. Bake for 28-31 minutes until the cheese is bubbly and edges are golden brown.

Remove from the oven and let cool for about 10 minutes. Slice into 8 pieces and serve warm with marinara sauce for dipping.