Put the blender jar together. Make sure you have a tight seal!

1/4 c vinegar (I use wine vinegar; type doesn’t matter, in my opinion)
1/4 c white wine
1 T minced green onion (use white part first - - or get fancy and use a shallot)
1 T tarragon (I use dried. If you use fresh, start with 1/2 T)

Boil until about 2 t remain. (More than 1 T [3 t] will result in a thin sauce.) Don't let the solids burn! Set a sieve over the blender jar and strain the essence directly into it. Press solids with a spoon to squeeze out all of the essence.

When cooled (about 10 minutes - - though the essence can wait as long as needed), add:

3 egg yolks

1 c melted butter (I use half a stick of butter and top up with olive oil)

Melt the butter (or use oleo; or combine with olive oil - - I've never used straight olive oil, but why not?). Be careful not to splatter it all over the microwave! I melt it in 10-second pulses ahead of time and "hold" it on power setting 1. It's plenty warm to create a warm sauce. Whir the egg yolks and essence in the blender. Here's the tricky bit: add the hot butter in droplets until you have about 1 T added. Then you can progress to a thin stream. Continue in this way until you hear the blender "change speeds." This means the emulsion of the egg yolks and oil has been made, and you can pour in the rest of the butter.

Yum!

Notes:

• Allow 3 minutes from the time you start the sauce to serving time. If you're steaming broccoli (the traditional Béarnaise Transporter), get it going and close to done before the 3-minute mark.
• I use salted butter and don't add extra salt.
• Supposedly, one is not to use the "white solids" at the bottom of the melted butter, but I always do.
• Put the lid on the blender and remove only the little cap in the middle of the lid to minimize splattering.
• I sometimes eliminate the white white and substitute about 2 t more of the vinegar. Since there's less liquid, I have to watch the infusion more carefully so that it doesn't burn.
• I have used dried minced onion in place of the green onion with no problem. Taste isn't greatly altered.
• Don't start with too much essence. This puts you at a disadvantage for thickening! No more than 1 T!
• I don't know if this works in the food processor. Sorry.
• I have made béarnaise from Egg Beaters. It's thin, though.
• Sometimes I eliminate the white wine in the essence. I don't see that it makes that much difference. You also can skip the vinegar and use only white wine, but this removes the acidic "bite" from the sauce. You might like it better this way!

Troubleshooting:

• sauce is too thick: thin with a little vegetable oil
• sauce won't thicken: Your problem is that you added the melted butter too quickly. Pour the sauce out of the blender jar except for 1 T. Add 1 T lemon juice (I use - - gasp! - - bottled lemon juice, and it works fine). Start the blender. Add the sauce just as if you were adding melted butter.
• sauce curdles ("turns"): use same technique as if the sauce won't thicken