Add water, cinnamon, allspice, cardamon, cloves, and lemon peel to a medium saucepan. Bring to a boil. Remove from heat, add tea bags, steep for 5 minutes. Remove tea bags.

Return to a low heat, Add lemon juice, orange juice, and brown sugar. Heat gently until warmed through. Taste and add more sugar if desired. Remove spices and peel.

Ladle into mugs, add rum if desired. Grate fresh nutmeg on top and add a lemon slice.