How to Thicken Slow Cooker Soup

The fastest reliable method: a cornstarch slurry

To thicken slow cooker soup quickly, mix cornstarch with an equal amount of cold water until smooth. Start with 1 tablespoon of cornstarch and 1 tablespoon of water for about 4 cups of soup. Stir the slurry into the hot soup during the last 15 to 30 minutes, then cover and let it heat through. Add more only if needed; the soup will continue to firm slightly as it cools. Never sprinkle dry cornstarch directly into the cooker, or it may form lumps.

Puree part of the soup

For a thicker soup without adding a separate starch, remove 1 to 2 cups of the cooked vegetables, beans, or broth and blend until smooth. Stir the puree back into the slow cooker. An immersion blender can also be used directly in the pot, but blend only part of the soup if you want to keep texture. This works especially well for lentil, bean, tomato, squash, potato, and vegetable soups.

Use potato or beans for body

Stir in a few spoonfuls of plain mashed potato during the final 20 to 30 minutes. It thickens the broth and gives it a hearty texture; add gradually to avoid making the soup gluey. Mashed or pureed beans work similarly in chili, bean soup, and vegetable soups. Choose a matching variety when appearance matters, such as white beans for a pale soup.

Add cream near the end

Heavy cream, half-and-half, evaporated milk, or softened cream cheese can make a soup feel thicker and smoother, though dairy adds richness more than firm thickening. Stir it in during the last 10 to 15 minutes on Low. Avoid prolonged high heat after adding dairy, which can cause separation. For a dairy-free finish, unsweetened coconut milk can work in soups with compatible flavors.

Reduce uncovered when it is safe

If the soup is fully cooked and your slow cooker manual permits uncovered cooking, remove the lid and let excess liquid evaporate on High, checking and stirring occasionally. This can take 20 to 45 minutes depending on the amount of broth and the cooker. It is most useful before adding delicate ingredients or dairy. Do not rely on reduction to cook raw meat safely; check that poultry reaches 165°F / 74°C and ground meat reaches 160°F / 71°C.

• Add starch late so it does not lose strength during long cooking.
• Do not dump dry flour into the soup; whisk flour with cool liquid first, or use a slurry.
• Taste after thickening, then adjust salt, pepper, and acidity.