Spray a large soup pot with Pam. Add the stock and bring to a boil. Turn down the heat to medium-low, and add the rice and blanced almonds. Cover and let cook slowly for 30 minutes.
Meanwhile, spray a 10-inch skillet with Pam, and in it melt the butter over medium heat. Add the onion, and saute until it starts to soften, about 3 1/2 minutes. Lower the heat slightly, and add the garlic. Continue cooking, stirring constantly, to soften the garlic for about 20 seconds. Stir in the sherry, then crumble in the almond paste a bit at a time. Remove the skillet from the heat, and whisk well to smooth it out.
Lower the heat under the stock to the barest possible simmer. Add the onion mixture, the orange zest, and evaporated skim milk. Let cook to blend flavors, 10 minutes more.
Puree the soup, in batches, in a food processor, then put through a food-mill or power strainer. Season to taste with salt and white pepper.
Reheat just before serving, and serve, very hot, in small cups. Garnish soup with toasted almonds and the merest bit of orange zest.