Here are a few tips to make the perfect sauce:
#1: Choose firm eggplants
Over-mature ones often have a more bitter flavour. Keep eggplant moist while roasting; fill a shallow pan with water and place in bottom of oven.
#2: Avoid rubbery mushrooms
Cook in batches over relatively high heat. If the pan is too full or the heat is too low, mushrooms steam versus brown. For best flavour, use a mix of mushrooms such as shiitake and portobello, and throw in a few seasonal mushrooms, such as late-summer chanterelles.
#3: Timing is crucial
Make sure shallots and garlic are soft before adding in rosemary, chili and umami powder.