In a bowl, whisk the eggs together with fish sauce, half of black sesame seeds, and chopped Thai chili. Season with salt and pepper if necessary. Pour half of the mixture into a big frying pan with hot oil to make a crepe. Add half the prepared mushroom mixture on one side of the crepe, then fold it in half to form an omelette. Repeat the process and make another omelette with the remaining egg and mushroom mixture.