In a large nonreactive saucepan set over medium-high heat, place the brown sugar, lemon slices, cloves, cinnamon stick, nutmeg, ginger, and water. Stir frequently to dissolve the sugar. Let the mixture come to a boil, turn the heat down to medium, and simmer for 10 minutes. Add the brandy and ale and heat but do not boil. Serve in beer mugs, with a lemon slice in each drink.