Heat your Instant Pot on sauté mode. Once it's hot, add vegetable oil, followed by onion and garlic. Sauté for a minute or two, then add the ground beef. Cook until the beef is browned and the onions are translucent.
1 tablespoon vegetable oil, 1 small onion, 1 tablespoon minced garlic, 1 pound ground beef
Remove and drain the beef, then return it to the Instant Pot. Add the frozen mixed vegetables, Worcestershire sauce, salt, and pepper. Mix well and sauté until the vegetables thaw and cook through.
1 bag frozen mixed vegetables, 2 tablespoons Worcestershire sauce, pinch salt, pinch pepper
While the vegetables are cooking, add melted butter, flour, and beef broth to a bowl. Mix well.
2 tablespoons salted butter, 2 tablespoons flour, ½ cup beef broth
Pour the mixture over the beef and veggies and stir to combine. Once it begins to thicken, transfer the contents of your pressure cooker to a casserole dish.
Clean the inside of your Instant Pot and add water to it, along with peeled and cut russet potatoes. Add salt to the water and potatoes and cook on high pressure for 8 minutes. Carefully quick-release the pressure when 8 minutes are up.
3 medium russet potatoes
Drain the water from the pot, then place the potatoes back inside. Using a hand mixer, mash the potatoes until smooth. Add butter and milk and beat through before adding salt and pepper.
1 teaspoon salt, ½ stick salted butter, 1½ cups whole milk, 1 teaspoon pepper
Transfer your mashed potatoes to the casserole dish, spreading over top of the beef and vegetable mixture.
Sprinkle with shredded cheddar cheese, then place it under your oven broiler for 5 minutes, or until golden brown. Serve and enjoy!
1½ cups shredded cheddar cheese