In a large pot, brown the beef with the onions and minced garlic on high heat while constantly stirring. This will break up the brown beef evenly and cook the onions and garlic evenly.
Once the ground beef is browned and the onions are translucent, drain the fat using a colander, leaving some of the fat in to aid in cooking the mushrooms.
Reduce heat to medium-high. Add in the mushrooms and continue to cook for about 5 minutes or until the mushrooms are soft and the juices have come out.
Add in the corn starch and stir well until well combined.
Add in the green beans, corn, salt, black pepper, white pepper, cinnamon, nutmeg, allspice, Worcestershire sauce, onion powder, garlic powder, parsley, Chicken or beef bouillon (If not using chicken or beef broth). Stir until well combined.
Add in the milk, and water (or chicken or beef broth instead of water). Stir continuously until the sauce begins to boil, and it has thickened slightly. Reduce the heat to low. Add in the bay leaf, and let the mixture simmer for 15 minutes while covered. Once the mixture is done simmering remove the bay leaf and toss it.
Preheat oven to 400 F.
Once the mixture is done simmering, grab an 11 x 7 baking dish. Pour in the beef mixture at the bottom of the dish and level it evenly. Ladle in small scoops of the mashed potatoes on top of the beef mixture. Using a spatula, gently spread the mashed potatoes over the beef mixture making sure to cover all the nooks and crannies. You can find the complete recipe for creamy mashed potatoes at PeacefulLivingNH.com.
Bake in a 400 F preheated oven for 30 minutes or until hot and bubbly and the top begins to brown.