Running out of one ingredient does not have to end the meal. The trick is knowing what a given ingredient is actually doing in the recipe — adding fat, acid, sweetness, structure, or aroma — and replacing that function rather than the exact item.

Aromatics

• Onion → shallots, leeks, or the white parts of green onions. Use slightly less; shallots are sharper.
• Garlic → garlic powder at roughly one quarter teaspoon per clove, added later in cooking so it does not scorch.
• Fresh herbs → dried herbs at one third the volume, added earlier so they have time to rehydrate.

Fats and dairy

• Butter → olive oil for savoury cooking, coconut oil or ghee where you want the richness back.
• Milk → oat, soy, or almond milk. Unsweetened only, or your sauce turns dessert-like.
• Sour cream → plain yoghurt, stirred in off the heat so it does not split.
• Heavy cream → evaporated milk, or whole milk thickened with a small amount of cornstarch.

Sweeteners and acids

• Sugar → honey or maple syrup at about three quarters the volume, with slightly less liquid elsewhere.
• Lemon juice → lime juice, or white wine vinegar at roughly half the amount.
• Fresh tomatoes → canned tomatoes; one 400 g can stands in for about four medium fresh tomatoes.

Eggs, in cooking but not in baking

In a binding role — meatballs, fritters, patties — one tablespoon of ground flaxseed with three tablespoons of water does the job. In custards, meringues, and most cakes, eggs are doing structural work that plant-based swaps only partly replicate, so expect a different result.

Three swaps to avoid

• Baking powder for baking soda, or the reverse. They react differently and are not a one-to-one exchange.
• Bread flour for cake flour in delicate bakes. The protein difference shows up as toughness.
• Dried beans for canned beans without adjusting time and liquid. Dried beans need hours, not minutes.