Place an oven-safe skillet (or cast iron skillet) over medium-high heat. Add the chopped onion and pepper, and cook until the vegetables start to soften, 4-5 minutes.
Crumble the ground beef into the skillet and stir with the veggies. Cook until the beef is browned through, about 5 minutes.
Stir the paprika, salt, and ground pepper into the skillet.
Sift the flour into the skillet and stir into the beef and veggies. Cook for 1-2 minutes, then stir the broth and cream into the skillet.
Bring the casserole filling to a simmer and cook until the mixture thickens, 3 to 4 minutes. Stir in the chopped parsley, dill, and thyme, along with the mustard.
Stir in the corn and peas. Taste the casserole mixture and add any additional salt and pepper, to taste.
Turn off the stove and remove the skillet from the heat.
Arrange the tater tots in a single layer over the top of the casserole mixture, making sure that the top is completely covered.
Bake the Beefy Tater Tot Casserole at 425F until the tater tots are browned and crispy, and the casserole is bubbling, about 20-30 minutes.
Remove Beefy Tater Tot Casserole from the oven and let sit 5 minutes before serving.