First, slice the sourdough bread. Using a serrated knife slice 1" vertical strips through the bread 3/4 of the way down. Be sure to not fully slice the bread, you want to keep the loaf intact. Once you've cut vertical strips across the entire loaf, slice 1" horizontal strips across the bread. You will then have 1" cubes of bread, still intact, and perfect little pockets ready for stuffing with deliciousness.
In a medium-size bowl combine crumbled feta cheese, shredded mozzarella (reserving a small handful for the top) sliced olives, crushed garlic, and fresh dill. Stir until well combined.
Melt butter in the microwave or in a small saucepan over medium-low heat. Whisk za'atar into butter and set aside.
Place your bread on a large baking sheet. Prepare the bread by first pouring half of the butter mixture over the bread, separating the cubes a bit to get the butter in between.
Next stuff the feta olive mixture between the cubes. I find that hands work best here. Really try to get the mixture dispersed evenly among the cubes.
Sprinkle the reserved mozzarella on top and cover the bread with the remainder of the butter mixture.
Bake in the oven for 18 minutes or until the cheese is melted and the bread is lightly browned.
Top with extra sliced olives, fresh dill, and fresh thyme. Serve hot.
Leftovers:Store leftovers in the fridge, when you are ready to reheat wrap the loaf in tin foil and place back in the oven for 15-20 minutes to reheat.Za'atar:If you can't find za'atar spice (read more about za'atar in this post) you can sub dried thyme and dried oregano.