Heat olive oil in a skillet over medium heat. Sauté onions and garlic until fragrant. Add gyros meat, oregano, paprika, salt, and pepper. Cook until meat is browned and fully cooked.
Assemble Casserole Base:
In a greased baking dish, layer rice or pasta (if using), then add cooked gyros meat, diced tomatoes, cucumbers, and bell peppers.
Make Garlic Hollandaise:
In a heatproof bowl over a pot of simmering water (double boiler), whisk egg yolks and lemon juice until thickened. Slowly drizzle in melted butter while continuously whisking until smooth. Stir in minced garlic, and season with salt and pepper.
Top the Casserole:
Pour garlic hollandaise evenly over the assembled casserole.
Bake:
Preheat oven to 180°C (350°F) and bake for 15–20 minutes, until the sauce is bubbly and slightly golden on top.
Garnish & Serve:
Remove from oven, sprinkle with fresh parsley/dill and crumbled feta if desired. Serve hot, optionally with extra shredded lettuce or tzatziki on the side.
Serving & Storage Tips:
