Heat oven to 400 degrees. Start a big pot of water to boil, so that it will be boiling by the time the dough is ready.
In a small pot, boil the 1/2 cup of water and 1/2 cup of the butter together until the butter is completely melted. Add the flour and take off the heat. Stir in the flour until all the dough pulls away from the pan and forms a ball. Add in eggs *one at a time*, waiting unil it is completely incorporated before you add the next egg. Add the spinach(make sure that the water is completely pressed out of the spinach!) and about a cup of shredded gruyere. Mix until all incorporated.
Place the other 1/2 cup of butter in the pan you will be using to bake the gnocchi(a 9x13 would probably work, I usually use an oval corning ware dish) Place the dish in the oven to melt the butter.
Drop the dough by tablespoon full into the boiling water(try to keep them in a uniform shape, mine usually come out looking like little eggs), remove the dough from the water about 30-60 seconds after they rise to the top. Place them in the dish with the melted butter and roll them around to coat with the butter. Pour the cream over the gnocchi. Dice up the remaining cheese and drop into the cream with the gnocchi.
At this point you can refridgerate the gnocchi until you are ready to stick it in the oven. I haven't tried freezing it, because I'm not sure how it would work with the cream.
Bake for about 45 minutes, until the top is browned and bubbly.