Fry the Vegetables:

1. Heat some oil in a pan over medium heat.
2. Add the chopped onion, minced garlic, and bell pepper. Sauté until soft and fragrant.
3. Set aside to cool slightly.

Mix Eggs and Kefir:

1. In a mixing bowl, beat the eggs and mix with kefir or yogurt.
2. Season the mixture with salt, black pepper, and chili flakes.

Assemble the Casserole:

1. Drain the potatoes and pat them dry with a tea towel.
2. Place half of the potato slices at the bottom of the greased baking dish.
3. Layer the sautéed vegetables over the potatoes, then place the remaining potato slices on top.

Add the Egg and Cheese Mixture:

1. Pour the egg-kefir mixture evenly over the potatoes, making sure it seeps into the layers.
2. Sprinkle the grated cheese generously on top.

Bake the Casserole:

1. Place the dish in the preheated oven and bake for 45-60 minutes, or until the potatoes are tender and the cheese is golden brown and bubbly.

Garnish and Serve:

1. After baking, let the casserole cool slightly.
2. Sprinkle with chopped parsley for a fresh touch and serve warm.