In a large saucepan, combine the sweet potatoes and enough cold water to cover. Bring to a boil, salt the water and cook until tender, 15 minutes. Drain and set aside, reserving the pot.
While the sweet potatoes cook, preheat the oven to 425°. In a deep skillet or Dutch oven, heat the EVOO, 2 turns of the pan, over high heat. Add the turkey and cook, breaking up with a spoon. Stir in the onion, carrots, celery and poultry seasoning. Season with salt and pepper and cook for 5 minutes.
In a small saucepan, melt 2 tablespoons butter over medium heat. Whisk in the flour for 1 minute, then whisk in the turkey broth and season with salt, pepper and the Worcestershire sauce. Simmer for a few minutes until thickened, then stir into the turkey mixture. Stir in the peas and remove from the heat.
Add the remaining 2 tablespoons butter to the sweet-potato pot and melt over medium-low heat. Add the sweet potatoes and banana; season with salt, pepper and the hot sauce and mash until combined.
Top the turkey with the sweet potato mixture and smooth the top. Cover the sweet potatoes with the cheddar and bake until the cheese is completely melted, about 5 minutes.