For the sweet potato gnocchi: Bring a large pot of water to boil. Add the potatoes and boil until fork-tender, about 15 minutes. Remove the potatoes with a slotted spoon (reserve the pot of water) and allow to cool for about 10 minutes.
Put the potatoes through a ricer into a bowl. Add the flour to a separate bowl and make a well. Add the oil and ice water and knead into a dough, adding in the cinnamon, nutmeg and salt. Fold in the mascarpone. Slowly add the potatoes and knead until the dough comes together and rolls out smoothly, 5 to 7 minutes. Form into a ball, wrap in plastic and let the dough rest for 10 minutes.
Bring the pot of water back to a boil. Roll the dough into a long thin log, then divide into 2-inch pieces. Boil the gnocchi until they float, 2 to 3 minutes.
Preheat the oven to 375 degrees F.
For the sauce: Melt the butter in a saucepan over medium heat and whisk in the flour until incorporated. Add the milk and cheese and season with salt and pepper. Cook until the cheese is fully melted and the sauce is thickened, about 7 minutes. Season with additional salt and pepper if needed, and stir in the cinnamon and nutmeg.
For the fried sage: In a heavy, shallow pan, add some canola oil and heat until a thermometer inserted in the oil registers 400 degrees F. Add the sage leaves and fry until crisp, 1 minute. Transfer to a plate lined with paper towels.
For the panko topping: Mix together the breadcrumbs, Parmesan and butter in a small bowl.
Combine the gnocchi and sauce gently in a bowl. Divide the mixture among individual 6-ounce ramekins. Top each with some panko topping, a fried sage leaf and extra Parmesan. Bake until bubbling and crispy brown on top, about 5 minutes. Serve in the ramekins.