Toast coriander seed, cumin seed, allspice berries, and black peppercorns in a dry skillet over medium heat until fragrant, about 1 minute. Grind into a fine powder, then mix with ginger powder, cinnamon, kosher salt, and smoked paprika.
Tear maitake mushrooms into large clusters and toss with olive oil and shawarma spice until evenly coated.
Heat a skillet over high heat and sear mushrooms until deeply caramelized on both sides. Transfer to a 350°F oven and roast until crispy and golden brown, about 12 to 15 minutes.
In a bowl, combine skyr, grated garlic, lemon zest, lemon juice, and salt, then whisk until smooth and creamy.
Cut Persian cucumbers into bite-sized pieces, toss with sumac, salt, and olive oil, and let sit for 10 minutes to lightly macerate.
Warm pita in a dry skillet or oven until soft, then brush with olive oil and sprinkle with za’atar.
Spread lemon yogurt onto a plate or shallow bowl, top with sumac cucumbers and roasted mushrooms, finish with mint, parsley, and dill, and serve with warm pita on the side.