Heat oven to 450 degrees. Cut away the flat bottom of the sea-urchin shell with scissors; pour away liquid. Scrape out membrane with the end of a spoons handle. Set aside the six most attractive urchins in a baking dish. Scoop the flesh out of the remaining six to yield about 1/2 cup. Pulse in food processor for 5 to 8 seconds. Add butter, and blend until thoroughly emulsified; add more butter if necessary. Press the urchin-butter mixture through a sieve with a spatula. Bake the whole sea urchins 4 to 5 minutes. Meanwhile, combine stock, cream, cayenne, salt, and pepper, to taste, in a small saucepan over medium heat. Add urchin-butter mixture, stirring constantly, until resulting emulsion thickens. Adjust seasoning; add lemon juice. Remove sea urchins from oven. Arrange them on a bed of seaweed, drizzle with Sea Urchin Butter, and garnish with lemon halves. Serves 2. Source: "Martha Stewart Living Magazine, Feb 1997" S(Formatted for MC5): "by Lynn Thomas - Lynn_Thomas@prodigy.net" Per serving: 852 Calories (kcal); 95g Total Fat; (97% calories from fat); 2g Protein; 4g Carbohydrate; 259mg Cholesterol; 31mg Sodium Food Exchanges: 0 Grain(Starch); 0 Lean Meat; 0 Vegetable; 0 Fruit; 19 Fat; 0 Other Carbohydrates Recipe by: Martha Stewart Converted by MM_Buster v2.0n.