In a large saucepan over medium heat, combine half-and-half, clam juice and white wine. In a separate saucepan, melt butter. Add shallots and saute until translucent. Add flour to butter mixture, stirring until flour is absorbed. Cook, stirring constantly, 2-3 minutes. Add heated half-and-half mixture all at once to the shallot mix, stirring constantly with a wire whip to remove any lumps. Add spinach, artichokes, shrimp, cayenne and black pepper and bring to a boil. Reduce heat and simmer 3 minutes, stirring occasionally, so the mixture does not scorch. Remove mixture from heat, and stir in cheese, if desired. Pour dip into bowl and serve hot.