Steak Sandwiches with Arugula, Caramelized Shallots, and a Sweet Creamy Sauce

5 from 1 vote

At least 3 hours, up to a day before you plan to cook and eat this meal, get your steak marinade ready.
In a bowl whisk together marinade ingredients.
Your steak can be in large pieces but it needs to be able to fit into a large skillet, so if the pieces are too long, cut them in half.
Add skirt steak (I used 2 steaks, 1 lb. each) to a large ziploc bag. Pour marinade over steak and refrigerate for 3 hours up to 24 hours.
When ready to cook, heat a large nonstick or cast iron skillet to medium-high heat (takes about 3-4 minutes to get the pan hot).
Once the pan is hot, add a thin layer of olive oil to the pan (about 2 tablespoons).
Using tongs, slowly lower a large piece of steak onto the skillet. It should sear and can pop so be sure to cover it right away. Let it cook covered on each side for about 5-6 minutes (depending on thickness). I like the edges to be slightly charred, and the inside just barely done. You can cook as little or as long as you'd like to get your steak to your perfect "done-ness".
*Steak can also be grilled to desired done-ness.
(All steaks will vary in size and thickness, so after searing on each side for 5-6 minutes, you can test with a steak knife.)
Once cooked, remove with tongs to a large cutting board. Cover with aluminum foil and let rest for 5 minutes.
Once rested, cut into thin strips with a very sharp knife. Set aside until ready to assemble sandwiches.

Before cooking the steak, it's nice to get the spread and onions ready. Do this while the steak is still marinating.
Whisk together all spread ingredients in a small bowl, tupperware, or Mason jar. Seal and refrigerate until ready to serve.

Before cooking the steak, it's nice to get the spread and onions ready. Do this while the steak is still marinating.
Add 1 tablespoon of olive oil to a small or medium-sized nonstick skillet, over medium heat.
Once the oil is hot, add the sliced shallots. Use a spatula to stir for a minute and coat them lightly in the oil.
Then slowly add enough water to just barely cover the bottom the pan, up about a 1/4" – add the cover and let the shallots steam for 5 minutes.
After 5 minutes, check again and stir. Let the water cook down. Once it has evaporated, add more water, cover and cook again, checking until the shallots have caramelized and reduced down. They should reduce by over half. Once soft and reduced down, set aside until ready to assemble your sandwiches.
The caramelized shallots store well in the fridge for a couple days.

To each slice of bread, or bun, add a layer of caramelized shallots on the bottom. The add a slice of cheese, then steak, then a handful of arugula, then spread the creamy mustard sauce on the top piece of bread. Press the sandwich together and enjoy!
For a large crowd you can leave all the sandwich ingredients out and let everyone build their own.
Enjoy these delicious sandwiches!