Bring a large pot of lightly salted water to a boil. Cook gnocchi in the boiling water until tender, about 5 minutes. Drain.
Once gnocchi goes into the boiling water, start the sauce: Melt butter in a saucepan over medium heat. Add shallots and cook until tender, about 3 minutes. Stir in cream and heat to almost a boil. Gradually mix in Fontina and Parmesan cheeses, being careful not to boil. Stir until smooth, then remove from the heat immediately so the sauce doesn't clump.
Place gnocchi into serving dishes and spoon sauce over top. Garnish each serving with basil.
