Place potatoes into a large pot, fill with water to 1 inch over potatoes. Add in 1 TBS salt. Bring to a boil over high heat. Lower heat to a medium and let simmer until potatoes are fork tender about 15-20 minutes (depending on size of potatoes).
Drain potatoes and put back into pot. Mash potatoes and add butter, milk, salt & pepper to taste. Set aside.
Heat 1 TBS cooking oil in a large skillet over medium high heat. Add onion and saute for 2 minutes until softened. Add in garlic and cook an additional 1 minute.
Add in ground beef, break it up and brown until no longer pink and cooked through. Drain.
Add to the cooked ground beef in skillet, 2 TBS butter and 2 TBS flour. Stir to coat for 2 minutes. Add in Worcestershire, beef broth, and black pepper. Stir and cook for 2 additional minutes to thicken. Turn off burner and stir in frozen peas, carrots, and corn.
In a 9 x 13 baking dish pour meat mixture in and spread evenly. Top with the mashed potatoes and spread evenly. Sprinkle with paprika, if desired.
Bake in preheated 375 degree oven for 20 minutes until heated through and mashed potatoes are golden. Enjoy.