Preheat oven to 375°F (190°C). Grease a 9x13-inch baking dish.

Chop the cooked bacon; shred the chicken into bite-sized pieces. Have the tater tots ready on their bag.

In a medium saucepan, melt 3 tbsp butter over medium heat.

Whisk in 2 tbsp flour and cook for 1 minute to remove the raw flour taste.

Slowly whisk in 1 cup milk until smooth. Bring to a gentle simmer, whisking until it thickens (about 2–3 minutes).

Stir in 1/2 cup ranch dressing. Season lightly with pepper; skip extra salt until you taste, since bacon and ranch are salty.

In a large bowl, combine shredded chicken, most of the chopped bacon (reserve a tablespoon for topping), and half of the shredded cheese. Pour the warm ranch sauce over and mix until evenly coated.

Spread the mixture into the prepared baking dish in an even layer. Arrange tater tots in a single layer on top. Sprinkle remaining 3/4 cup cheese and the reserved bacon over the tots.

Bake uncovered at 375°F for 30–35 minutes, until cheese is melted and tots are golden. If you want extra browning, broil for 1–3 minutes — watch closely to avoid burning.

Let rest for 5 minutes before serving to allow the sauce to set slightly.