Combine 2 pounds shredded boneless chicken breast with 10.5 ounces cream of chicken soup, 1 cup sour cream, 1 cup shredded sharp cheddar cheese, 1/2 cup diced yellow onion and seasonings at room temperature. Stir with a spatula for 2 to 3 minutes until evenly coated. Scrape the bowl sides halfway through and fold until the mixture looks thick and creamy. You'll see the cheese strands throughout the filling and smell the garlic as it blends. Miss this mixing window and the sauce won't coat every bite evenly. Fold gently for 3 minutes, keeps the filling structure balanced before slow cooking.

Spread the creamy chicken mixture into a 6-quart slow cooker and cover it with 32 ounces frozen tater tots at 35°F from the freezer. Arrange the tots in a loose layer for 5 minutes while leaving small gaps between pieces. The filling should sit evenly below the potato topping. You'll see the orange-golden tater tots against the pale creamy mixture. (I tried stacking the tots too tightly once. The center stayed soft instead of getting the texture I wanted.) Keep the topping loose and spaced, allows heat to move through the casserole.

Cook the layered casserole on low heat for 4 to 5 hours until the chicken filling reaches 165°F and the cheese melts completely. Keep the lid closed and avoid stirring during the first 3 hours. The edges will bubble gently and the tater tots will soften with golden patches forming on top. You'll notice the cheese aroma filling the kitchen. Go past 5 hours and the filling can dry around the edges. Slow cooking at low heat for 4 hours keeps the chicken moist and the sauce stable. Preheat the oven to 375°F now so it's fully hot by the time the pan goes in.

Transfer the casserole to a 375°F oven-safe baking dish and bake uncovered for 15 to 20 minutes until the tater tots become crisp. Spread the surface gently with a spoon to keep the topping uneven. You'll see deeper golden edges and hear a light crisp sound when the topping sets. The cheese should look glossy between the potato pieces. Miss this final heat step and the top stays softer than expected. Bake uncovered at 375°F, dry heat creates the crisp surface texture.

Scoop one portion of the casserole onto a white plate at 165°F serving temperature after resting for 10 minutes. Use a gentle lifting motion so the tater tots stay on top and the creamy layers remain visible. The portion should show crispy potato pieces, melted cheese and thick chicken filling. You'll smell the baked cheese and see small golden variations across the surface. Cutting too soon can make the sauce spread before serving. Rest 10 minutes after baking, lets the layers settle for cleaner portions.