Choose your substitute based on the dish type and desired flavor match. Use the bowl-over-pot for emulsions, the saucepan insert for custards and cheese, and the microwave for quick small-batch melts.
Prepare the substitute as directed: fill the pot with 1-2 inches of water for stove methods, or cut solids into small even pieces for the microwave method.
Apply the substitution ratio carefully. Keep the bowl base 1-2 cm above the waterline for stove methods, or start with 10-15 second microwave bursts at 50% power and stir between each.
Taste and adjust seasoning. Some methods transfer heat faster than others, so monitor closely and remove from heat when the sauce reaches the desired consistency.