Preheat the oven to 400 degrees F (200 degrees C). Line a baking sheet with foil. Place sweet potatoes on the baking sheet and prick all over with a sharp knife.

Bake in the preheated oven until tender when pierced with a knife, about 1 hour. Let sit until cool enough to handle. Do not turn off the oven.

Place bacon in a cold pan over medium-high heat, and cook until fat begins to render; stir and reduce heat to medium. Continue to cook, stirring occasionally, until the fat is fully rendered out and bacon is browned and fully cooked. Drain off bacon fat, and reserve for another use. 

Scoop sweet potatoes into a mixing bowl, discarding the skin. Use a spoon to break the chunks of sweet potato into smaller, more uniform pieces. The texture can be as smooth or coarse as you like.

Add the salt, black pepper, smoked paprika, egg, sour cream, green onions, half of reserved bacon, and two-thirds of cheese. Stir together until everything is evenly mixed. 

Distribute mixture evenly into a shallow 2-quart baking dish, but leave the surface roughly textured. Scatter on the remaining bacon, followed by remaining cheese.

Bake casserole in the preheated oven until the top is browned, and the casserole is heated through and bubbling around the edges, 30 to 35 minutes.

Serve with more sliced green onions and sour cream if desired.