Classic Steak Diane with Microwave-Steamed Baby Potatoes

Wash 600g baby yellow potatoes and cut them in half. Place them in a microwave-safe bowl with 2 tbsp water, cover with a microwave-safe plate, and microwave on high for 8 minutes until fork-tender. Toss with 10g unsalted butter, a pinch of salt, and 5g finely chopped fresh flat-leaf parsley, then cover to keep warm.

Pat dry 1.2 kg raw beef sirloin steaks with paper towels. Season both sides generously with 1 tsp salt and 1 tsp black pepper.

Finely mince 2 shallots and 2 garlic cloves. Slice 200g cremini mushrooms. Finely chop 10g fresh chives and the remaining 5g parsley.

Heat 2 tbsp olive oil in a large skillet over medium-high heat. Add the steaks and sear for 3 to 4 minutes per side for medium-rare, building a deep brown crust (fond) on the bottom of the pan. Transfer all the steaks to a warm plate to rest.

Reduce the skillet heat to medium. Add the remaining 20g unsalted butter, then add 200g sliced cremini mushrooms. Sauté for 4 minutes until golden. Stir in 2 minced shallots and cook for 2 minutes until soft. Add 2 minced garlic cloves and cook for 30 seconds, stirring constantly to prevent burning.

Pour in 60 ml cognac to deglaze the pan, scraping up all the caramelized bits from the bottom. Simmer for 1 to 2 minutes until the liquid is reduced by half.

Whisk in 120 ml beef broth, 1 tbsp Dijon mustard, and 1 tbsp Worcestershire sauce. Simmer for 2 minutes. Reduce heat to low and stir in 120 ml heavy cream. Simmer gently for 2 minutes until the sauce thickens slightly; season with salt and pepper to taste.

Slice the rested steaks. Divide exactly half of the cooked steak (600g) among 3 serving plates alongside the steamed baby potatoes. Spoon the warm mushroom Diane sauce over the steak on the plates, and garnish with 10g chopped chives and the remaining parsley.

Allow the remaining 600g of cooked steak to cool completely, then place it in an airtight container and store in the refrigerator for tomorrow's Day 4 lunch salad.