Pat rib-eyes dry. Drizzle extra-virgin olive oil across each side of the steaks then season them with grill seasoning blend and reserve.
Prepare chimichurri: pile the herbs together and finely chop. Coarsely chop 2 cloves of the garlic, reserving one large clove left cracked away from skin but whole. Add coarse chopped garlic to herbs and mill them together, chopping even finer, then transfer to a small bowl. Add in the finely chopped red onions and the zest of 1 lemon. Once the lemon has been zested, cut it into wedges and reserve. To the herbs and onions, add 3 tablespoons (eyeball it) red wine vinegar, a splash of water and about 1/3 cup extra-virgin olive oil. Stir to combine the chimichurri and reserve.
Fill sink or large bowl with cold water. Remove stems from spinach and add to water. Agitate the leaves to release the grit attached to the leaves. Repeat this process, testing leaves as you go until they are free of sand. Dry in a salad spinner or on layers of paper towels.
Heat a large nonstick skillet over medium-high heat. Add 2 tablespoons extra-virgin olive oil, 2 turns of the pan, then add in the chipotle in abobo, sliced onions and mushrooms. If you are using powdered chipotle, add onions and mushrooms first then season with the powder. Cook the mushrooms and onions, stirring frequently, 10 minutes. Do not add salt and pepper – the salt will draw liquid out of the mushrooms, slowing up the browning process.
Heat a heavy bottomed pan and sear the steaks for about 4 to 5 minutes on each side for medium rare to medium. Add 2 minutes for medium to medium well doneness. Once cooked, let meat rest 5 or 10 minutes for juice to redistribute.
Once the mushrooms are tender, coarsely chop the spinach and fold into the pan in bunches until wilted and incorporated fully. Season the mixture with salt and pepper and remove from heat.
Char bread under broiler, rub it with the remaining clove of garlic, butter the bread and sprinkle with chives. Place the toasted bread on plates and top each slice with a whole steak. The bread will catch meat juices as you dine. Top the steaks with a few shakes of Worcestershire and generous spoonfuls of chimichurri. Serve mountains of smoky mushrooms and spinach alongside the steaks.