I made this butter (from epicurious.com) last night to serve with swordfish (but I think it'd work with other fish as well) and it was incredible, one of the best things I've ever tasted (even though I didn't use prime ingredients) - and it couldn't be simpler. The key to having it not separate (a complain with some of the reviews in epicurious) is to start whisking as soon as you add the balsamic vinegar, and to whisk briskly after each ingredient. Don't forget to season appropriately at the end - it's the salt which really brings out the flavor of this butter.
Balsamic Butter for Fish
- 1/2 cup unsalted butter
- 3 Tbsp. balsamic vinegar
- 1 Tbsp. honey
- 1 Tbsp. Dijon mustard
- salt to taste
Heat the butter in a small saucepan over medium heat until it starts boiling, about 6 minutes. Remove from heat. Immediately whisk in the balsamic vinegar, honey and mustard. Season with salt. Serve immediately or reheat (while whisking) prior to serving.