Place silicone mold with 15 (1 1/2-inch) half-sphere cavities on rimmed baking pan; line separate rimmed baking pan with parchment paper. In small bowl, whisk cinnamon, allspice, cardamom, ginger, cloves and pepper. Makes about 3 tablespoons.
In medium microwave-safe bowl, heat chocolate chips in microwave oven on high 1 minute or until melted, stirring every 20 seconds. Brush insides of 12 molds with chocolate to coat, making sure to coat all the way to the rims; freeze 5 minutes or until hardened, then unmold onto parchment-lined pan.
Heat small nonstick skillet over very low heat 3 minutes or until slightly warm. Place 1 sphere, open side down, in skillet 2 seconds or just until edge is slightly melted. Transfer sphere back to pan, open side up; fill with 1 1/2 teaspoons cinnamon mixture. Place second sphere in skillet, open side down, 2 seconds or just until edge is slightly melted; place on top of filled sphere, open side down, to make ball shape. Repeat with remaining spheres and cinnamon mixture to make 5 more bombs; cool completely.
Place bombs in 6 large mugs. In medium saucepan, heat milk to a simmer; pour over bombs and stir to combine. Add 1/8 teaspoon of extract to each mug; stir to combine.
Chef's Tip: Refrigerate hot chocolate bombs in an airtight container up to 2 weeks. Any symmetrical-shaped 1-tablespoon capacity silicone mold can be used.