one 10-12 ounce NY strip steak (set out at room temperature for 20-30 minutes)
salt and pepper for seasoning steak
1/3-1/2 loaf baguette, batard or ciabatta (as needed)
butter as needed for sliced bread before toasting
2 tablespoons olive oil
5-6 ounces sliced shiitake mushrooms
approx. 5-ounces fresh baby spinach
3-4 teaspoons soy sauce
3-4 tablespoons mayonnaise
approx. 3 - 4 teaspoons wasabi powder (or more to taste)
Cut the bread you're using horizontally in half from top to bottom, lightly butter the cut sides and then place those into a cast iron skillet and lightly toast the cut sides underneath the broiler.
Once the bread is lightly toasted, take that out of the skillet and place the salt and pepper seasoned steak into the skillet and back underneath the broiler.
You'll want the broiler set to the high temperature setting and you'll want to use tongs to flip the steak a couple of times as it's cooking. It'll take around 8-10 minutes to cook to medium-medium rare for a 1 1/2-inch thick steak.
Once the steak is cooked to your liking, take it out of the skillet to rest on a clean plate and add a splash of olive oil to the skillet on the stovetop burner and sauté 5 ounces of sliced shiitake mushrooms to soften.
At that point, add a big handful of baby spinach and let that cook along to wilt down.
Then add a little splash of soy sauce and turn the heat off.
Besides thinly slicing the steak after it has rested for 5-10 minutes, you'll want to make the wasabi mayonnaise by combining 3-4 tablespoons mayonnaise with wasabi powder to taste.
Spread the mayonnaise over the cut sides of the toasted bread, top that with the thinly sliced steak and finish with the shiitake mushrooms and spinach.
Use other types of mushrooms instead of shiitake.
Serve with a fork and steak knife.