"Create a beginner-friendly recipe for Cosmic Brownie Cookies yielding 24 cookies using these ingredients: all-purpose flour, unsalted butter, brown sugar, semi-sweet chocolate chips, heavy cream, egg, granulated sugar, cocoa powder, whole milk, vanilla extract, cornstarch, baking soda, sea salt, and candy-coated rainbow chips. Make it suitable for a household of 4, metric units only, and keep it simple and practical for home baking in Riverside/Jurupa Valley, CA cottage-food style: shelf-stable finished cookies, no perishable frosting or fillings, clear storage guidance, and standard home-kitchen equipment only (oven, stovetop, microwave)."