In a large skillet, heat a drizzle of oil over medium heat. Add the ground beef and cook for 6-8 minutes until browned.

Mix in the sliced mushrooms and sauté for an additional 5 minutes until softened.

Lower the heat to medium-low, stir in the shredded cheese, and let it melt for 2-3 minutes.

In a medium bowl, combine the Greek yogurt, diced cucumber, minced garlic, and lemon juice. Season with salt, pepper, and dill.

Warm the pita breads in the microwave or skillet until pliable. Slice each in half to create pockets.

Fill each pita pocket with the cheesy beef and mushroom mixture, then drizzle with tzatziki sauce.