To make the best grilled steak, your grill pan should be heated very hot before cooking the steak. You can marinate the steak a day ahead. The steak should be rest at room temperature at least for 10 minutes before cooking. If light soy sauce is not handy to you, you can just season your steak with salt and pepper. But the soy sauce would help keep your steak moist after grilling.
220 gm rump steak (or sirloin steak), at room temperature
3 potatoes, washed, with skin on, cut into 1½ cm dices
a knob of butter
2 Tbsp vegetable oil
6 button mushrooms, thinly sliced
100 gm mixed salad vegetables
2 Tbsp whole egg mayonnaise sauce
1 tsp wholegrain mustard
1 tsp water
1/2 tsp sugar
1 Tbsp light soy sauce
2 tsp Worcestershire sauce
1 tsp Shaoxing wine or sherry wine
pepper, to taste
Coat the steak with the marinade evenly and leave for about 5 minutes.
Cook diced potatoes into salted boiling water for about 15 to 20 minutes, until tender. Drain well.
Meanwhile, heat a grill pan over high heat for 3 minutes. Add butter and oil. When the butter starts to melt, cook the steak over medium high heat, for 4 minutes each side for medium-rare, or until cooked to your liking. Remove from the pan and cover with foil to keep warm.
While cooking the steak, mix all the ingredients of mustard sauce in a small bowl. Set aside.
Add the mushrooms in the pan and cook until tender. Add the cooked potatoes and stir them to absorb all the juice and bits left in the pan. Season the mushrooms and potatoes with salt and pepper.
Slice the beef and divide them onto serving plates, on top of the salad vegetables, with mushroom and potato dices, drizzle over mustard sauce and serve.
Recipe by Lifehack at http://www.lifehack.org/articles/lifestyle/20mins-meal-grilled-steak-with-mustard-sauce.html