Preheat the oven to 300 degrees Fahrenheit. Simmer the onions in butter until cooked. Add the rice and cook, stirring, for 2 minutes. Add the saffron and white wine and stir until the wine is absorbed. Start adding the broth, 1/2 cup at a time, waiting for each addition to be absorbed before adding another 1/2 cup.
Continue until the rice is tender or "al dente". Add the butter, then season with salt and pepper. Remove from the heat and pour into a small, 2-inch deep pan, or put into ramekins, smoothing over the tops and put into a refrigerator until cold.
If using the pan, cut the risotto into circles with a 2 3/4-inch biscuit cutter, if using ramekins, remove the rice carefully, retaining the disk-shape.
Heat a sautée pan and add 2 Tablespoons of canola oil. Sauteé the rice cakes until golden brown on both sides. Put in the oven for 10 minutes over to insure the cakes are heated through.
Season shrimp with salt and pepper. Sautée in butter, heating to about 350 degrees Fahrenheit. Turn shrimp over when pink. Add mushrooms, shallots, garlic, and green onion and sautée for about 4 minutes.
Add sherry and simmer 1 minute. Add cream; shake pan until sauce is thickened.
Garnish with parsley.
