Steak with mushrooms and tarragon butter sauce

• Slice the onion into half rings.
• Heat a drizzle of olive oil in a wok or deep frying pan over high heat and fry the onion and mushrooms for 4 - 6 minutes. 
• Deglaze with the vinegar and soy sauce, and season with salt and pepper.

Did you know...mushrooms are a great source of vitamin B2, which helps keep you energised. Vitamin B2 is most commonly found in animal products, so if you follow a vegetarian or vegan diet it's good to eat mushrooms regularly so as to prevent deficiency.

• Meanwhile, melt a knob of butter in a frying pan over medium-high heat. When the butter is nice and hot, fry the steak for 1 - 3 minutes per side.
• Finely chop the tarragon and slice the garlic.
• Add the tarragon, garlic and a knob of butter per person to the pan in the last minute of frying the steak to make a butter sauce.
• Finely chop the parsley and mix with the potatoes.