~NOTE~ I use Rosemary Focaccia Bread for the buns which can be made up a day ahead of time or several weeks ahead of time if frozen. The recipe makes 2 loafs, but I divide the dough to make 8 buns. If you don't have time to make the focaccia buns, then regular buns can be used.
In a large mixing bowl, combine bread and milk and allow to sit for several minutes.
Squeeze the milk from the bread and discard milk.
In the same mixing bowl, combine the wet bread, ground beef, garlic, parmesan cheese, oregano, parsley, red pepper flakes, pepper, and salt.
Mix ingredients by hand to combine well.
Divide meat mixture into 4 and form 4 patties about 3/4-inch to 1-inch thick.
In a large skillet, heat 2 tablespoons olive oil with butter.
Once butter is melted, add sliced red onions and saute until tender, but not brown.
Remove onions from skillet and place on a plate.
Place patties in hot skillet.
Cook patties 5-6 minutes on each side, or until done to your liking.
While patties are cooking, you can toast the buns, if desired.
Just before patties are done, place 1 slice of provolone cheese and 1 slice on mozzarella on top of each patty and allow to melt.
Remove patties from skillet and place them on paper towels to drain.
Place each patty on a rosemary focaccia bun.
Top each patty with a slices of roasted red bell pepper and a few grilled onions.
Serve open face and allow your guest to dress up their burgers with the condiment of their choice - such as lettuce, tomatoes, mayo and mustard.