Brown Butter Mayonnaise

Directions

1. To make brown butter: In a small skillet or saucepan over medium heat, melt the butter completely; cook until it turns brown and smells nutty, about 4 to 6 minutes. Be sure to stir frequently, scraping up any bits from the bottom so they don't burn. Take the pan off heat and transfer the brown butter to a glass measuring cup with a spout. Let cool to just above room temperature.
2. To make mayonnaise: Combine egg yolk, lemon juice, cold water, and salt in a medium mixing bowl. Whisk until well integrated and bright yellow, about 30 seconds.
3. Whisking constantly, add about half of the brown butter to yolk mixture, a few small drops at a time, over the span of about 4 minutes. Resist the urge to add the brown butter too quickly; you want a nice emulsion to form. Gradually add remaining brown butter in a very slow, thin stream, whisking constantly, until mayonnaise is thick and spreadable, about 4 additional minutes. Taste for seasoning and balance. (Compared to mayonnaise made with oil, the brown butter version will be slightly less thick. I’m presuming this is due to the water content in the butter.)
4. Note 1: you can use a mini food processor or hand blender to make mayo (and I assume that this brown butter version is no different). Generally, I find the old fashioned whisk-by-hand method to be the most reliable and satisfying – and it yields a silkier-textured mayonnaise in my opinion.
5. Note 2: if your mayonnaise breaks or doesn’t thicken enough, you can save it! Empty your mayonnaise into a glass measuring cup with a spout. Whisk 1 yolk (at room temperature) and another drop or two of lemon juice in your mixing bowl. Whisking constantly, add the broken mayonnaise drip by drip to the yolk mixture until it starts to thicken, then add the remainder in a slow, thin stream.
6. Cover and chill. It should keep 2 to 3 days. It'll thicken considerably once cold due to the butter; take out of the refrigerator and let warm to cool room temperature, stirring well to restore your smooth, spreadable consistency, before you plan to use. Get ready to use it on everything.