In a small bowl, mix together diced tomatoes, basil, balsamic, olive oil, garlic, salt and pepper. Set aside and let flavors marinate.
Whisk eggs in a medium bowl until no streaks of egg remain. Then whisk in the milk and pinch of salt and pepper.
Drop a piece of the thickly sliced bread into the custard and let sit for 20-30 seconds on each side. Then dunk each slice in Parmesan in a shallow bowl. Coat each side with the cheese. Set aside on a plate. Repeat with remaining bread slices.
In a large skillet over medium heat, melt 2 Tbsp. unsalted butter and cook bread slices for 3-4 minutes each side or until golden brown. Repeat this with remaining bread and use more butter in pan if needed.
Top each slice with a slice or two of prosciutto and some of the tomato mixture. Garnish with a drizzle with balsamic reduction and flaky salt if desired. Enjoy!