Heat the oven to 425F. Scrub and dry the sweet potatoes, prick each one a few times with a fork, and bake them directly on a rimmed sheet for 45 to 55 minutes, until a knife slides in with no resistance.

Cool 10 minutes, then halve each potato lengthwise and scoop out the flesh with a metal spoon, leaving a wall about ¼ inch thick attached to the skin. Save the scooped flesh for another use.

Raise the oven to 450F. Brush both faces of every shell with olive oil and season the cut faces with the kosher salt and smoked paprika.

Lay the shells cut side down on the sheet and bake 8 minutes. Flip them and bake 8 more, until the rims have firmed and curled slightly.

Melt the butter in a small saucepan over medium-low heat, then take the pan off the heat.

Whisk the hot sauce into the butter a splash at a time, letting each addition go smooth before the next, then whisk in the garlic powder and black pepper.

Pull the cooked chicken into ragged shreds, pour the sauce over, and fold it through. Let it sit 3 minutes so the shreds absorb the sauce.

Spoon the buffalo chicken into the shells, filling each one level with the rim rather than above it.

Scatter the grated cheddar over the chicken and broil 2 to 3 minutes, watching constantly, until the cheese is melted and spotted gold.

Whisk the Greek yogurt, blue cheese, milk, and lemon juice together until pourable. Drizzle it over the hot skins in thin lines, scatter the green onions, and serve at once.