Preheat the oven to 375 degrees F.
In a large frying pan over medium meat, melt the butter; add mushrooms, onion, carrots, red bell pepper, yellow or orange bell pepper, and garlic. Cook 10 minutes, stirring often, until the moisture from the vegetables has evaporated; set aside to cool.
In a large bowl, combine the salt, black pepper, white pepper, cayenne pepper, fresh herbs, nutmeg, and egg; beat well. Add the ketchup and half-and-half; blend thoroughly. Add the ground beef and bread crumbs to the egg mixture. Then add the cooled vegetable mixture and mix thoroughly with your hands (do not over mix or the loaf will become heavy and tough). NOTE: If meat mixture is too moist, add additional bread crumbs.
In a large baking dish, form the meat mixture into an oval approximately 4 1/2-inches wide by 1 1/2-inches deep (resembling a long loaf of bread).
Bake 30 to 40 minutes or until meatloaf reaches an internal temperature of 160 degrees F. (do not overcook or it will be dry). Remove from oven and let the meatloaf rest approximately 15 minutes before serving.
Makes 8 to 10 servings.
Garden Meatloaf Recipe: https://whatscookingamerica.net/beef/gardenmeatloaf.htm