What a fantastic long weekend. Cottage, company and food. Had these sirloins with caramelized onions and mushrooms with my twice baked potatoes, what a treat! We were all stuffed, but not so stuffed that we couldn’t have s’mores later while watching the fireworks.
Combine the garlic purée and mustard. Place the steak on a flat surface and pat dry with paper towels, then massage the garlic mixture into the steak. Season the steak with salt and pepper. Cover and set aside at room temperature for 30 to 45 minutes.
Preheat the grill to medium–high (450°F/230°C).
Place the wok — or a heavy sauté pan — on the side burner and heat over a high flame. Melt the butter and olive oil to sizzling and add the sliced onions. Sauté to soften, about 3 to 4 minutes. Add the mushrooms and continue sautéing until the mushrooms have softened and any moisture has evaporated. Stir in the minced garlic, sauté for another 3 minutes, and then move pan over to the grill. Let the mixture slow–sauté over the grill, stirring frequently, until the onions have turned a deep golden brown, about 15 minutes. Do not let the onions brown too fast or they will burn instead of caramelizing.
Add the vinegar and stir until it is absorbed. Stir in the sugar and season with salt and pepper. Set the onion mixture aside and keep warm.
Place the steak on the grill and cook for 5 to 6 minutes a side for medium rare. Remove from the grill and let rest for 3 to 4 minutes.
Thinly slice the steak across the grain. Place slices on a platter or individual plates and top with the onion mixture. Serve immediately.
The only words I can say will be said by yourself and the people you share this recipe with when you cook it. And really it’s rather non-sensical noises of happiness than words. Cook it and see for yourself.