Indian Railway Omelette Sandwich

Name: Indian Railway Omelette Sandwich
Ingredients: 4 large eggs; 1 tablespoon whole milk; 1/2 medium onion, peeled and finely chopped; 2 green chiles, seeded and finely chopped; 2 sprigs cilantro, finely chopped; 1/4 teaspoon black pepper; 1/4 teaspoon chile powder (you can also use red pepper flakes); 1/4 teaspoon ground turmeric; 1 pinch kosher salt; 1 splash vegetable oil or ghee; 4 slices white bread or pav