Nearly every mistake made in the kitchen can be corrected, with the exception of burned food. An overly-pungent onion, although not a culinary mistake, can overpower the taste buds as well as other flavors in a dish, detracting from the whole preparation. An onion's pungency correlates with its allicin content — the sulfuric compound responsible for an onion's strength. Although it is ideal to tame an assertive onion flavor early on when creating a meal, certain measures, such as adding an absorbent vegetable, can be used during the cooking process. Other methods that temper an onion's flavor include marinating it in milk, sweating it in oil and substituting it with a less-pungent variety.
Peel the onions and cut them in half. Place the onions in a food-storage container or a heavy-duty food-storage bag that can be sealed.
Cover the onions with cold whole milk. Lactose helps temper the allicin — a sulfuric compound — in the onion.
Marinate the onions in the milk for 45 minutes. Rinse the onions with cool running water and pat them dry with paper towels before using.
Heat 1 tbsp. of olive oil per cup of onions in a saute pan over low heat for five minutes. Place the onions in the pan.
Cut a circle of parchment paper large enough to fit over the onions and place it on them. Alternatively, place a piece of wax paper over the onions. The goal is to loosely cover the onions while allowing them to release their moisture.
Sweat the onions until translucent, approximately eight minutes. Discard the paper and drain the onions on paper towels before proceeding.
Substitute a pungent onion for a milder variety. If using white onions, widely held as the most piquant, substitute an equal amount of yellow onions, next on the list in terms of pungency.
Substitute purple or red onions for yellow onions, which are slightly less spicy than the yellow varieties, and far less spicy than white varieties.
Substitute shallots for red or purple onions. Shallots have a mildly sweet onion taste and a hint of garlic in the finish.
Substitute cipollini or pearl onions for shallots. Cipollini and pearl onions have a flavor slightly redolent of onions that leans more towards sweet than pungent.
Peel one whole Russet potato and place it in the sauce or soup. Starchy potatoes, such as Russets, absorb more liquid than waxy potatoes, such as Yukon Golds.
Cook the potato with the sauce or soup for one hour.
Remove the potato and discard. Potatoes simply absorb liquid, and do not selectively reduce the allicin content of the dish. However, as opposed to removing a quantity of liquid and replacing it with an equal amount of water — a common solution to an overly salty or pungent dish that causes the loss of herbs, spices and aromatic ingredients — the potato assimilates only the liquid, including the pungent moisture released by onions during cooking, and leaves other ingredients intact.