Rinse quinoa under cold running water. Combine quinoa and chicken stock; heat to boiling. Reduce heat to medium low and cook, covered, until all liquid has been absorbed and the quinoa looks transparent, 12 to 15 minutes. Toss in 1 tablespoon of butter with a fork. Cook lettuce in boiling, salted water for 5 minutes. Drain. Blend in food processor and process until smooth. Melt remaining butter in medium size saucepan over medium low heat. Add flour and cook stirring constantly, 2 minutes. Whisk in the milk and cream and cook until very thick, 2 minutes. Add the cayenne pepper, nutmeg and sugar. Add the lettuce and cook 1 minute longer. Combine the cooked quinoa with the lettuce mixture and season with salt and pepper.