Heat the oven to 375°F and lightly grease a 1 1/2-quart baking dish.
Blend cottage cheese and softened cream cheese for 45 to 60 seconds, scraping once, until mostly smooth.
Blend in hot sauce and ranch seasoning just until the color is even.
Transfer to a bowl and fold in cooked chicken, 3/4 cup cheddar and half the scallions.
Spread in the dish, top with remaining cheddar and bake 18 to 24 minutes until bubbling at the edges and 165°F in the center.
Rest 5 minutes, then finish with remaining scallions and optional blue cheese.