In a large pot, melt 2 tablespoons of butter over medium-high heat, then sauté the bite-sized chicken pieces until cooked through and golden. Remove and set aside.

Add remaining butter to the pot, melt it, and then add the diced onion, sliced celery, and sliced carrots. Cook until tender and fragrant.

Stir in minced garlic and cook for an additional minute until fragrant.

Sprinkle flour over the vegetable mixture, stir well and cook for about 1 minute. Gradually add chicken broth and milk, whisking continuously. Simmer for about 5-7 minutes until thickened.

Add thyme, nutmeg, salt, pepper, cooked chicken, peas, and corn, mixing well.

Transfer the mixture to a greased 9x13 baking dish, spread evenly and top with cheddar cheese.

Arrange frozen tater tots in a single layer on top of the cheese filling.

Bake in a preheated oven at 400°F (200°C) for 40-45 minutes until the tater tots are golden brown and the filling is bubbling.