Onion Sauce

This onion sauce gets its luxurious body from an ingredient most cooks overlook: bone marrow. Pureed with microwave-softened onions and beef stock, it creates a sauce that’s incredibly silky and rich without flour or cream thickening it.

The onions cook unpeeled under a damp paper towel in the microwave, which steams them soft in eight minutes flat. Peeling them after cooking is easier than before, and the onions develop a sweeter, mellower flavor than raw-start sauteing gives you.

A splash of dry sherry at the end adds acidity and a faint nuttiness that keeps the sauce from tasting heavy. Fresh chives snipped over the top bring color and a sharp onion bite that contrasts the smooth puree.

This is a classic pairing for roast beef, but it works just as well spooned over grilled steaks or mashed potatoes.

Pro Tips

• Ask your butcher to split the marrow bones lengthwise for easier extraction. A quick microwave blast loosens the marrow so it slides right out.
• Puree thoroughly with a hand mixer or immersion blender. Any remaining lumps will give the sauce a grainy texture instead of the velvety finish you want.
• Taste the sauce after adding the sherry before salting. The beef stock and marrow both carry salt, so you may need less than you think.

Variations

• Red wine version: Replace the sherry with a full-bodied red wine and reduce for an extra minute before pureeing.
• Herb finish: Stir in fresh thyme leaves or tarragon instead of chives for a different aromatic profile.
• No-marrow option: Substitute the bone marrow with a tablespoon of butter for a lighter but less complex sauce.