01
Shallots
10.0best for soup1 cup : 3/4 cup
Stronger, use less and mince fine
10.0
onions substitute
in soup.
Onions simmered in Soup adds body, flavor, and nutrition to every spoonful. The substitute should cook down at a similar rate and add comparable texture.
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adjustment for this dish
Shallots go in at 0.75 cup per cup and sauté in 10 minutes (shorter than onion's 15) because they brown faster from higher sugar content. They deliver more delicate depth to the broth and dissolve fully during simmer, which means less need to blend for body — stir 1/2 cup back in instead of 1 to thicken.
02
Carrots
10.0best for soup1 cup : 1 cup
Sweet and aromatic when diced and sauteed; classic mirepoix swap in soups
10.0
adjustment for this dish
Carrots swap 1:1 and bring natural sweetness instead of onion's Maillard depth, so add 1 teaspoon tomato paste during the sauté to mimic the savory base. They hold shape longer in a 90-minute simmer than onion and won't thicken the broth via pectin, so reduce by 30% rather than 20% to concentrate the stock properly.
03
Leeks
6.71 cup : 3/4 cup
Stronger flavor, use slightly less
6.7
adjustment for this dish
Leeks substitute at 0.75 cup and are the classic French aromatics base — sweat 12 minutes in butter over low heat to build depth without browning, which would muddy the broth. Use whites and light greens, sliced 1/4 inch, and skim the first 5 minutes of simmer because leek proteins foam more than onion.
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04
Celery
6.71 cup : 1 cup
Aromatic base vegetable, milder but similar role
6.7
adjustment for this dish
Celery replaces 1:1 but contributes water rather than sweetness, so sauté 18 minutes (3 more than onion) to drive off moisture and concentrate flavor before you add stock. Pair with 1 bay leaf and extra aromatics because celery alone can't carry the body onion provides; blend 1.5 cups of the pot to thicken the broth.
05
Cabbage
6.71 cup : 1 cup
Mild sweet bulk for braises and stews when sauteed; won't build the same aroma base
6.7
adjustment for this dish
Cabbage swaps 1:1 by volume and contributes body through dissolved fiber rather than onion's pectin, which means a cloudier broth. Shred to 1/4 inch, sauté 10 minutes to remove raw sulfur notes, then simmer with a bay leaf for at least 30 minutes — undercooked cabbage stays rubbery and refuses to thicken the stock.
06
Bell Pepper
6.71 cup : 1 cup
Diced bell pepper adds sweetness and crunch; good aromatic base in stir-fries
6.7
07
Onion Powder
3.31 tsp : 1 tsp
Use 1 tsp onion powder per small onion; provides concentrated flavor without bulk or moisture
3.3
08
Garlic
3.33 cloves : 1 cloves
Strong allium, use few cloves for aromatic base
3.3
09
Fennel
6.71 cup : 1 cup
Mild anise when raw, sweet onion-like cooked
6.7
10
Chives
3.31/4 cup : 1 cup
Mild onion flavor, best added at end raw
3.3
technique for soup
technique
Onions are the first aromatic into nearly every soup pot because their slow 15-minute sauté builds the Maillard base that gives the broth its depth — skip that step and you're left with thin stock even after a 2-hour simmer. Start with 1 cup diced onion per quart of stock, sweat in 2 tablespoons fat over medium heat, and stir every 90 seconds so the sugars brown evenly without scorching.
Add a bay leaf and warm liquid only after the onions have gone deep amber. Unlike the crisp-tender onion of a stir-fry, soup onions should break down completely and thicken the body through dissolved pectin — if you want a silky finish, blend 1 cup of the pot and stir it back in.
Skim any foam within the first 10 minutes of simmer; onion proteins coagulate early and will cloud the broth if left. Reduce by 20% to concentrate the sweetness the onions surrender into the stock.
pitfalls to avoid
watch out
Don't add onions to already-simmering broth; they need a dry sauté first to build the aromatics base or the stock stays thin and one-note.
watch out
Avoid chopping unevenly — bits under 1/4 inch scorch while 1/2 inch chunks are still raw, and neither will blend into the body smoothly.
watch out
Skim within the first 10 minutes of simmer because onion proteins coagulate early and cloud the broth with a grey film if left to reduce.
watch out
Reduce salt at the start and season near the end; a 90-minute simmer concentrates the sweetness the onions release and can push the pot past balance.
watch out
Don't blend the whole pot if you want texture — stir just 1 cup back in to thicken while leaving visible pieces for body and depth.