Preheat oven to 375 degrees Fahrenheit (190 degrees Celsius).

Slice cauliflower heads into steaks (you should be able to get three to four steaks per head, but if it falls apart, no worries. It will still taste great). Lay on a Gefen Parchment-lined baking sheet and drizzle with one tablespoon olive oil, one teaspoon salt, and half a teaspoon pepper. Roast for 35 minutes or until edges are browning and core is cooked through.

Meanwhile, preheat a large frying pan with the remaining tablespoon of olive oil. Sauté all mushrooms over medium-high heat until browned and no liquid remains, seasoning with salt and pepper.

Plate cauliflower on a large platter and heap with sautéed mushrooms.

Combine tahini, water, lemon juice, one-fourth teaspoon salt, and parsley, and drizzle over the cauliflower. Sprinkle with sumac for a floral/citrus garnish.