Preheat oven to 400 degrees Fahrenheit.
Place butter in large sauté pan over medium heat. As soon as butter is melted, add 8 fresh sage leaves to pan. Let infuse until butter has browned slightly, remove from heat. Remove sage leaves with a slotted spoon or tongs and reserve for later.
Return sauté pan with butter to medium-high heat and add cubed sourdough and garlic. Stir to coat bread in butter then allow bread to toast in butter. This may take up to 10 minutes, just keep an eye on the bread and stir as necessary so all sides of the cubes get nice and toasted.
Once bread cubes are toasted, set aside in a large bowl.
Next, prepare all other parts of the pudding. Whisk eggs in a small bowl; set aside.
To prepare prosciutto, heat up a medium sauté pan on medium-high heat with olive oil. Once pan is hot, add prosciutto and let it start to fry. Once prosciutto is crispy, remove from sauté pan and place on a plate lined with a paper towel to soak up some of the excess grease.
Chop up reserved, fried sage leaves as well as the 4 additional sage leaves that were not in the brown butter mixture.
Add beaten eggs, crispy prosciutto, sage, 1 cup shredded cheese, almond milk, nutmeg and salt and pepper to bowl with toasted bread cubes in it. Stir until combined. Pour bread mixture into a ceramic baking dish coated with non-stick cooking spray; top with remaining ¼ cup shredded cheese.
Bake bread pudding in 400 degree oven for 30 minutes. After 30 minutes, turn broiler on high and broil for an additional 5-6 minutes.
Remove from oven and let cool before eating.