Stir together 2 cups water, the sugar, gingerroot slices, cranberries (if using) cinnamon pieces, allspice, cardamom (if using) and cloves in a 2-quart or similar non-reactive saucepan. Bring to a boil over medium heat, stirring, then adjust the heat so the mixture boils gently. Boil gently, stirring occasionally, for 15 to 20 minutes. Remove from the heat and stir in the lavender buds. Let stand to steep at least 45 minutes, and preferably up to 4 hours for more intense flavor. (Or refrigerate, covered, and let steep overnight.)
Strain the steeped syrup through a very fine sieve into a large measure. Press down firmly to extract as much flavor as possible from the solids, then discard them. (For a clearer syrup, line the sieve with a slightly dampened double-thickness of cheesecloth before straining.)
Rinse out the saucepan and return the syrup to it. Bring the syrup to a boil. Boil for 2 minutes. Let cool and put the syrup in a clean, (preferably sterilized) bottle or jar with a non-reactive cap or lid. Refrigerate for 2 to 3 months. (Or freeze airtight for up to 6 months; thaw and keep refrigerated for 3 months.) Makes about 2 cups syrup.
Recipe by Nancy's Lavender Place at https://nancyslavenderplace.com/lavender-spice-mulling-syrup-for-pumpkin-spice-lattes/