Wash the leek and slice it into thin rings. Toast the tablespoon of pine nuts briefly in a dry frying pan until they turn light golden and set aside. Crack the three eggs into a bowl, add the thyme and beat everything with a fork until well combined.
Heat a knob of butter in the frying pan over medium heat. Add the sliced leek and sauté for a few minutes until the vegetable is soft. Then pour the egg mixture evenly over the leek in the pan and let the omelette cook gently until set.
Crumble the fifty grams of soft goat cheese as soon as the top of the egg is almost set. Place the cheese on one half of the omelette. Fold the other half over immediately using a spatula, so the residual heat can melt the goat cheese.
Slide the folded omelette from the pan onto a plate. Sprinkle the reserved toasted pine nuts on top and serve immediately.