Combine the lemon, sugar, and water in a small, 2 to 3-quart slow cooker set to high. Cover and heat, stirring occasionally, until the sugar dissolves completely, 20 to 30 minutes. Add the Scotch whiskey and stir to combine. Reduce the heat to low and serve warm with lemon slices and freshly grated nutmeg.
Recipe courtesy of Alton Brown, 2009