1 part butter (room temperature)
1 part oil (room temperature)
2-5 parts water (room temperature) (optional)
either finely chopped fresh herbs, or crushed dry herbs, to taste
Blend butter and oil together, add finely chopped herbs to taste, add water in drops (like you add oil when you make mayonnaise).
Can't say if you need to add some salt to this recipe, but I'm used to it, as Finnish butter always contains salt.
My favorite herbs to add to this: parsley, or lovage, or celeriac leaves, or fresh black currant leaves (Ribes nigrum) - Yum! Don't restrict yourself to garden-grown herbs, there's lots of good stuff growing in the woods and fields. And let your taste buds decide.
I make a larger batch and freeze what I won't use right away - if you add water this will only keep for about a week or so in the fridge.
Basil herb butter
From "Susan K. Wehe" <swehe.ix.netcom.com>
On using basil: mix with chives, parsley and butter to form an herb butter. Different basils create different tastes.
1/2 lb margarine
1 TLB chives
1 TLB parsley
1 TLB basil