Preheat the oven to 425°F. Bring a large pot of salted water to a boil for the cavatappi. Peel and roughly chop the shallot and garlic. Chop the broccoli florets into bite-sized pieces.
Add broccoli florets to a baking sheet and toss with 2 tsp olive oil and a pinch of salt and pepper. Roast until browned and crisp in places, about 5 to 8 minutes. Remove from the oven and toss in the Buffalo sauce until evenly coated.
Add the Banza cavatappi to the boiling water, stir, and cook until al dente, about 8 to 10 minutes. Drain and rinse, and return to the large pot, off of the heat. Place a medium oven-safe skillet over medium-high heat with 1 tbsp olive oil. Once hot, add the shallot, garlic, white miso paste, and a pinch of salt and pepper. Cook until the shallot becomes translucent, about 3 to 5 minutes.
Add oat flour to the skillet and cook, stirring frequently, until a film forms on the bottom, about 1 to 2 minutes. Lower heat to medium and add half the almond milk. Whisk until well combined and thickened, then add the remaining milk. Whisk and simmer until sauce thickens and coats the back of a spoon, about 2 to 4 minutes.
Add the sauce mixture to the blender along with the shredded cheddar and a pinch of salt. Blend until cheese sauce is smooth. Pour the cheese sauce over the cooked pasta in the pot. Stir to coat evenly, then transfer back to the oven-safe skillet.
Set oven to broil on high. Top the mac and cheese with the Buffalo broccoli and broil in the oven until the broccoli and cheese begin to brown, about 1 to 2 minutes. Serve family style, straight from the skillet.