Robert Sauce

Ingredients

• 2 whole Onions, medium size
• 1 oz Butter (for frying) (Approx. 2 tablespoons)
• 2 tbsp White wine vinegar or cider vinegar
• 1 cup Beef stock or water (Original calls for 'a very little', adjust for desired consistency)
• 1 tbsp Butter (for roux)
• 1 tbsp All-purpose flour (for roux)
• 2 tsp Fresh prepared mustard (Dijon or English) (Original calls for a dessertspoonful)
• 0.25 tsp Salt (To taste)
• 0.25 tsp Black pepper (To taste)

Instructions

1. 1Peel the onions and cut them into very small pieces (fine dice).
2. 2In a separate small saucepan, melt the roux butter. Whisk in the flour and cook over medium heat, stirring constantly, until the mixture turns a nutty brown color. Remove from heat and set aside.
3. 3In a frying pan, melt the frying butter. Add the chopped onions and fry them until they are soft and golden brown.
4. 4Drain off any excess butter from the onions. Add the vinegar to the pan and let it simmer gently for 10 to 15 minutes. This step is crucial to remove the harsh acidity of the vinegar.
5. 5Add the stock (or water) to the pan and stir well. Whisk in the prepared brown roux to thicken the sauce to your desired consistency. Simmer for a few minutes to blend flavors.
6. 6Remove from heat (or keep on very low heat). Stir in the fresh mustard, salt, and pepper. Serve warm.