SERVES 8 • 1 HR 15 MIN

2 tbsp. extra-virgin olive oil

1 large yellow onion, finely chopped

4 cloves garlic, coarsely chopped

Kosher salt

1½ lb. lean ground beef

Freshly ground black pepper

2 tbsp. unsalted butter

1 tbsp. all-purpose flour

¾ c. low-sodium chicken broth

1 (10.5-oz.) can cream of mushroom soup

½ c. frozen corn

½ c. frozen green beans

1 tbsp. Worcestershire sauce

1 tsp. yellow mustard (optional)

6 oz. extra-sharp yellow cheddar, grated (about 1½ c.), divided

1½ lb. tater tots (about 72)

Sliced scallions, for serving

1. Preheat oven to 375°. In a large skillet over medium-high heat, heat oil. Add onion and garlic and cook, stirring frequently, until lightly browned, 7 to 8 minutes; season with salt.

2. Add beef, breaking up into smaller pieces. Cook, stirring, until browned, 6 to 7 minutes; season with salt and pepper. Transfer to a medium bowl.

3. In same skillet over medium heat, melt butter. Add flour and cook, whisking constantly, until roux is bubbly and fragrant, 1 to 2 minutes. Slowly add broth, then whisk until mixture simmers and thickens. (There should be no lumps.) Stir in soup. 

4. Add meat mixture, corn, beans, Worcestershire, mustard (if using), and half of cheese; season with salt. Pour mixture into a 13″ x 9″ baking dish. Top with remaining cheese. Arrange tater tots in horizontal rows on top, leaving a small gap between each.

5. Bake casserole until center and edges are bubbling, 35 to 40 minutes. Top with scallions.

https://www.delish.com/cooking/recipe-ideas/a46305536/best-tater-tot-casserole-recipe/