Heat the half-and-half in a small saucepan over medium heat until barely simmering. Add the agave, cardamom, ginger, peppercorns, cloves, allspice and cinnamon; stir gently. Turn off the heat and let steep for 15 to 20 minutes. Strain.
Divide the chai mixture among four mugs. Add 1 1/2 cups coffee and 1 ounce bourbon to each mug; stir gently. Garnish with whipped cream and star anise.