Over medium heat, melt butter in a sizable skillet or saucepan. After it has melted, add beef liver and minced onion. Cook the liver and onion in the pan until they are both soft. In the last minute, add the minced garlic and simmer until fragrant.
Blend the liver, butter, onion, and garlic in a blender until smooth. If it's having trouble pureeing, you can add a little cream.
Blend all remaining ingredients in a blender until they are completely smooth. Adjust the salt as necessary after tasting.
Pate can be eaten right away with a crusty baquette or crackers, or it can be chilled and served in an airtight container.