In a bowl, whisk milk and dry mustard together until well blended. Add eggs, Parmesan cheese, salt, and pepper. In a separate bowl, combine bread, ham, tomato, cheese and basil. In a non-stick large muffin tin or popover pan, spray with cooking spray and load with the bread mixture. Pour egg mixture over bread mixture until eggs are evenly distributed or ⅔ full. Cover with plastic wrap and put in the refrigerator for at least one hour or overnight. In the morning, take them out of the fridge, preheat the oven to 350°F, and bake for 20-30 minutes until the eggs are set. Let sit in the pan for 5 minutes before removing to eat or save at room temperature or in the fridge. They’ll keep for up to 3 days. If you don’t eat them all the first day.