To make Sichuan Sweet Soy Sauce, bring 2 cups light soy sauce and 2 cups dark-brown sugar to a simmer in a medium saucepan over medium-low heat. Place 2 cardamom pods, 1 to 2 pieces of star anise, 1 piece cassia bark, a 1-inch-long ginger slice, 1 tsp fennel seeds, 1 bay leaf and 1 tsp whole Sichuan pepper in a spice bag. (If you don’t have a spice bag, add everything directly to the pot and strain when finished.) Add the spice bag to the pot and adjust the heat to the lowest setting. Simmer for at least 1 hour. Remove the saucepan from the heat and let the sauce steep overnight. Remove the spice bag and store the sauce in an airtight container in the refrigerator for up to 3 weeks.