Cook the potatoes, carrots, and garlic cloves in a big saucepan with enough water to cover, simmering until tender. Drain and add to a large mixing bowl. Season with salt and pepper, a few tablespoon of butter, and about 1/8 cup of milk. The potatoes should be a thicker consistency than if you were eating them as is. Mash to potatoes until the potatoes are smooth, lumps of carrots are ok. Taste and season again if needed.

While the potatoes are cooking brown the ground meat in a large skillet. Drain fat. Remove from pan and set aside. In enough oil to cover the bottom of the skillet saute onion and celery until tender. Add two tablespoons butter, flour, and mustard, stir for a minute. Slowly add in stock and stir or whisk until smooth. Add ground beef and Worcestershire sauce. Season with salt and pepper. Bring to a simmer for 3-4 minutes. Taste and season further if needed.

Steam the peas and corn, if you are using a pea, corn, carrot, and bean frozen mix, no worries, use those.

Preheat your oven to 400 degrees. In a deep-sided 8×8 in light greased with butter casserole pan, spread the meat mixture evenly across the bottom, the sprinkle the pea and corn mixture over top. Dollop the potatoes over top of the vegetables and spread out, roughing up the top with fork. Bake for 30-35 minutes until golden brown on top and bubbly. Put a baking sheet on the rack underneath to catch any drips. Let rest 5 minutes before serving. A salad on the side would be a perfect meal.