For the filling: In a large skillet, brown the ground beef over medium-high heat. Drain off any excess grease.
1.5 pound ground beef
Add the chopped onion and minced garlic to the skillet and cook until softened, about 5 minutes.
1.5 pound ground beef
Stir in the frozen peas, frozen corn, beef broth, tomato paste, Worcestershire sauce, thyme, pepper, and salt. Bring to a simmer and cook for 5 minutes, stirring occasionally.
1.5 pound ground beef
For the topping: While the filling is simmering, boil the potatoes in a large pot of salted water until tender, about 15-20 minutes. Drain well.
1.5 pound ground beef
Mash the potatoes with milk, butter, salt, and pepper until smooth and creamy.
1.5 pound ground beef
Pour the beef filling into a 9x13 inch baking dish.
Spread the mashed potatoes evenly over the beef filling.
Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and the filling is bubbly.
Let stand for 5-10 minutes before serving.
Notes
This recipe can be made ahead of time and reheated. For an extra rich topping, add a sprinkle of shredded cheddar cheese before baking.