Whisk the eggs with the chopped dill and minced garlic, then season with salt and pepper. Add the chilli flakes, if used.
Dice the halloumi into 1cm cubes.
Heat the oil in an oven-proof medium frying pan and fry the halloumi cubes until they are brown all over.
Pour in the egg mixture and let it spread out evenly. Scatter the peas on top.
Put a lid on and cook for about 5 minutes, then turn down the heat and cook until the egg is almost set.
Turn on the grill to high in the oven, then brown the frittata for a couple of minutes.
Scatter some more chopped dill on the top.
Let the frittata cool and cut it into wedges or squares.
Serve warm for a meal or at room temperature for nibbles.