When butter is bubbling, add the onions and chillies. Cook until translucent. Set aside and keep warm.
Beat the eggs lightly with a fork.
Melt the butter over medium-low heat.
Add the eggs. Allow the eggs to cook for a minute, then use a spatula to gently lift the cooked eggs from the edges of the pan. Tilt the pan to allow the uncooked parts to flow to the edge of the pan.
Cook for a few more seconds. Cook longer if you like it well done.
Fold the omelette in half. Slide it onto a plate with the help of a spatula. Garnish with cheddar cheese, followed by biltong, feta cheese, black pepper to taste and chives.