Identify whether your recipe needs the liqueur mainly for sweetness, chocolate flavor, or alcohol volume (cocktail vs. dessert).
Choose the closest match from the list: chocolate liqueur (closest), dark chocolate liqueur (richer), or coffee liqueur (mocha shift).
Use the listed ratio as your starting point, then taste and adjust: add cocoa for intensity or a touch more syrup for sweetness.
If using a homemade option (syrup + spirit or cocoa + syrup + extract), mix thoroughly and rest 5 minutes so flavors round out.
For cocktails, keep the substitute cold and build in small increments—liqueurs vary widely in strength and sweetness.