To make the salad , mix baby spinach, basil, mint, cucumber, tomatoes and peanuts in a salad bowl , dress and toss until all the flavors are infused with all the ingredients. 

To make the dressing , stir the olive oil, mustard and balsamic vinegar.

To cook the steaks, make sure they are at room temperature. Brush a ridged griddle pan with the oil and place over a high heat. When the pan is hot, add the steaks and cook for 1–2 minutes per side for rare, 2–2½ minutes per side for medium or up to 4 minutes per side for well done, depending on the thickness. Remove from the pan, cover with kitchen foil and leave to rest for 5 minutes at room temperature.

Serve the steak with the salad and top with toasted peanuts.