Step 1

To culture the cream, mix buttermilk and heavy cream in a glass jar. Cover loosely with a towel and let the jar sit in at room temperature for 24-48 hours. When the cream has thickened and tastes a bit tangy, it's ready to churn.

Step 2

Before churning the cream, make sure the cream is about 60F/15C.

Step 3

Using a stand or hand mixer, beat cream until it forms stiff peaks. Start on low to prevent splatters, then turn up to high. When the cream begins to look curdled, turn the mixer down to low. Stop when the cream has separated.

Step 4

Drain off as much of the buttermilk as possible (pour into a jar so you can use it later).

Step 5

Mix the ice with the water. Pour 1/2 cup of the cold water over the butter. Use a spatula to press or knead the butter against the side of the bowl. When the water becomes cloudy (it will happen quickly the first few times), drain the liquid. Then repeat the process with another 1/2 cup of water. Repeat until the water remains clear (3-5 times).

Step 6

Knead the butter against the side of the bowl a few more times to get as much water out of the butter as possible.

Step 7

If you'd like salted butter, mix in salt to taste.

Step 8

Store butter in an air tight container or wrap tightly in parchment paper. Use the butter within a week.