To make delicious mascarpone gnocchi you need to mix all 3 ingredients and kneed it into dough. Just enough for it to come together in a ball shape. It will start to feel sticky soon, because you are melting the cheese with your hands, so no kneading anymore at that point, just add flour to help with the shaping.
Roll it out into a rope shape and cut it to smaller pieces to get gnocchi. (you can split your dough to more pieces to make it easier to handle, in the process sprinkle with flour when it starts to stick).
Cook in hot, salted water just until they come to the surface, drain and serve with your favorite sauce.