Bacon Sauce

A cooked bacon-fat dressing thickened first with flour and then with egg yolks — essentially a savory hollandaise-adjacent sauce built on a roux instead of butter alone. The one thing that decides success is heat control at the end.

• The hinge: yolks off the heatPull the pan from the burner before the yolks go in, and beat them in a little at a time — or temper them first with a few spoonfuls of the hot base. Returned to a boil, they scramble and the sauce turns grainy past saving.
• "Paprica"An older spelling of paprika, used here for color and a faint warmth rather than heat; smoked paprika will overwhelm the bacon.
• Bacon fatFive tablespoonfuls is the rendered fat from roughly six to eight modern slices. Salt levels vary a good deal with the bacon, so hold the salt until the very end, as the recipe advises.
• Vinegar strengthFive tablespoons of vinegar to half a cup of water is sharp by current taste, and the recipe does not say what vinegar to use. Strengths varied then and vary now, so start with three tablespoons and add the rest to taste.
• The rouxTwo tablespoons of flour in five of fat is a slack roux. Cook it a full minute or two so it loses its raw taste, then add the liquid gradually to keep it smooth — it thickens quickly and can seize if the water goes in all at once.
• YieldThe fat, vinegar and water alone come to more than a cup before the yolks go in. It thickens as it cools and can be loosened with a spoonful of hot water.
• The greensDandelion, endive, chicory and corn salad (mâche) are all bitter or sturdy, which is why a rich, sour dressing suits them. On soft lettuce, use a lighter hand or the leaves collapse.