Cook fusilli according to instructions on the packaging. This should be approx 8-10 minutes. Leave to cool.
Soak onions in vinegar for about 3 minutes.
Mix mayonnaise, sweetened yoghurt, and mustard in a bowl. Add a teaspoon of olive oil, a generous pinch of black pepper and a pinch of salt.
Mix until all ingredients are well incorporated.
Remove onions from vinegar, run under water briefly and pat dry with a paper towel. Alternatively, you can let them drip off for about a minute in a sieve.
In a large bowl, add onions, fusilli, eggs, olives, ham, carrots, and cucumber and add the dressing.
Adjust salt as necessary and place the salad in the fridge until ready to serve.