Laced with assertive horseradish, this sauce makes a lively accompaniment to both poached eggs and crisp, buttery potatoes.
Melt butter in a small saucepan over medium. Place egg yolks and lemon juice in a blender; process until smooth. With blender running, gradually drizzle in hot melted butter until sauce is thickened, about 1 minute. Scrape butter mixture into a bowl; stir in horseradish. Season with salt and pepper, and serve immediately.