This is a killer sandwich — and that’s coming from a big sandwich lover. And guess what?It’s a Tyler Florence recipe. Big surprise, I know. There are so many awesome flavors going on here: garlic and rosemary on the steak, balsamic vinegar alongside the meaty portobellos and red onion, sharp fontina cheese and the most awesome aioli, bright with spicy arugula and acid from the lemon. Just awesome. All on some crunchy, chewy ciabatta. I could seriously eat this every single night. Try me.

TW’s Tips

• I had some pretty big shallots and found that the roasting time wasn’t sufficient to get them nice and tender — you want them well cooked and soft to the touch. If you have bigger shallots, cut them up or break them apart.
• You can make the mayo ahead — just keep in the fridge.
• Get some good quality fontina to really get the good flavor you want here.
• Be generous with the mayo — it’s delish.
• Be prepared — it’s a messy sandwich, but SO worth it!

Steak

• 1 head garlic
• 2 shallots
• Needles from 2 rosemary sprigs
• 1 bay leaf
• 1 cup + 2 tablespoons olive oil
• Salt and pepper to taste
• 1 1/2 pounds flank steak, preferably about 3/4 inch thick

Mayonnaise

• 3/4 cup mayonnaise
• Juice from 1/2 lemon
• 2 tablespoons horseradish
• 2 bunches coarsely chopped arugula
• Salt and pepper to taste

Everything Else

• 4 portobello mushroom caps
• 1 red onion, sliced
• 2 tablespoons balsamic vinegar
• 1/4 cup olive oil
• Salt and pepper to taste
• 1/4 pound fontina
• 1 loaf ciabatta bread, split horizontally
• 1 bunch arugula

Directions

Preheat the oven to 350 degrees. Remove the outer layers of skin from the garlic and shallot. Smash them open with the flat side of a knife to break up the cloves. Set both down on a reasonably sized square of aluminum foil. Drizzle the tablespoon of olive oil on top, and add the rosemary and bay leaf. Wrap securely in the aluminum foil. Place it on a pan if you want to be extra safe, and let it bake for 30 minutes.

While you’re waiting for your garlic and shallot to roast, start the mayonnaise. If you have a food processor, blend all of the mayonnaise ingredients together. Season with salt and pepper and pop in the refrigerator.

Once the garlic and shallot are done roasting, let them sit out to cool for a few minutes. Remove the bay leaf and carefully pour any juices into the food processor. Peel the garlic cloves and shallots and toss into the processor with 1 cup olive oil, salt, and pepper and pulse until well mixed. Coat both sides of the steak with the olive oil mixture. Set it in the refrigerator and let it marinate for at least two hours or overnight, flipping it halfway through.

When you’re ready to cook the steak, take it out to let it warm up a little while you slice your mushrooms and onions. Lay the mushrooms and onion slices in a shallow platter, drizzle with the vinegar and oil, and season with salt and pepper. Try not to break up the onion slices into rings, they are easier to grill as slices. Use a grill or heat up a pan over medium-high heat, and cook the steak for seven minutes on each side– you may need to adjust this time if your steak is thinner or thicker than recommended.

Once the steak is done, move it to a plate to let it rest for 10 minutes. Saute the mushrooms and onions over medium heat. Once they’re done, remove them from the pan (the plate you set the steak on is a good place to put them) and set your bread in the pan to toast. Slice the steak against the grain as thinly as you can.

To assemble the sandwich, spread the mayonnaise on the bread. Add the steak and veggies. Top with the cheese and a bit of arugula.