Sour Cream
From the message board of CountryLife.net Here are two methods for making your own sour cream at home.

Method 1
I N G R E D I E N T S
1 cup cream
1 tablespoon cultured buttermilk
Recipe can be increased at the ratio of 1 tablespoon buttermilk to 1 cup of cream.

I N S T R U C T I O N S
In a double boiler bring the fresh cream up to 180 degrees. Cool to room temp in a cold water bath. Add the buttermilk, cover, and let sit at room temp. for 24-48 hours. Stir and refrigerate. The batch will keep approximately 3-4 weeks, refrigerated

Method 2
I N G R E D I E N T S
1 cup cream
1 1/2 cups pasteurized whole milk
1/2 cup buttermilk

I N S T R U C T I O N S
Mix all the ingredients in a bowl over warm water. Raise the temperature of the mixture to (68 degrees to 70 degrees F) and let it stand for 12 to 24 hours or until it is sufficiently sour and thick enough to cling firmly to a spoon. Keep in the refrigerator until you want to use it. For a richer heavier sour cream combine 2 cups of pasteurized heavy cream with 5 tablespoons of cultured buttermilk and incubate as before. For better texture refrigerate for 24 hours before serving.

Fresh cream is fermented with live culture to make sour cream. The process is similar to making Dahi, taste is similar to Makhan

It is similar to making Dahi (Yogurt). The cream is fermented using live culture to make sour cream. You have to heat cream to 190º F to change the protein structures and then cool it down to 120° F before adding culture. We will use Ultra-pasteurized cream. The ultra-pasteurization process changes the protein structure eliminating need to heat it 190º F.

Commercial sour cream sold in the stores has no live culture.

This sour cream tastes almost like Makhan.

Ingredients

1. Heavy whipping cream Ultra-pasteurized: 1 Quart
2. Culture starter yogurt: ¼ cup
If this is your first batch, use commercial natural plain yogurt. Make sure it has live culture.

Method

Heat Whipping Cream in a pan to 120° F. Add Culture. Store in warm place (Ambient temperature 105° F) for six hours. Store it in Refrigerator.

Making Sour Cream To make sour cream, take one cup of fresh cream (or, if you don't have a milk cow, buy heavy whipping cream from the store). Mix it with one tablespoon of sour-cream (this is where the culture comes from).

You need to keep this mixture, in whatever container you mixed it in, at about 70 degrees for 24 hours. If the top of your fridge is warm you could set it there.... I just fill up a bowl with hot water and put the container in there (usually have to weight it down or it will float). After 24 hours it will have thickened considerably. (If not, the temperature was too low... just get it to 70 degrees and let it sit until it thickens). Then put it in the fridge. It is best to refridgerate it for 24 hours before using it.

Once you have your sour cream, you can use a tablespoon of it to get your next batch going...