Toast cinnamon, cloves, cardamom, coriander, and star anise in a skillet until fragrant.
Transfer spices to slow cooker and pour in apple cider.
Mull on high for 4 hours, reducing heat if cider begins to bubble.
Stir in brandy 10 minutes before serving. Add sugar if tart.
Ladle into mugs and garnish with lemon, nutmeg, or extra brandy.
