Romanesco, sometimes also known as romanesco cauliflower or romanesco broccoli is a beautiful vegetable, bright green in colour with a striking pattern. It has also a delicate and nutty taste that you can truly appreciate in this Italian quiche.
Replace romanesco with regular cauliflower or with broccoli. You can also use a mixture of Greek yogurt with a splash of cream instead of mascarpone.
Parmesan cheese is not truly vegetarian, as it contains animal rennet. To make this dish 100% vegetarian, omit the cheese or find a suitable vegetarian substitute made without animal rennet. In supermarkets look for the 'parmesan style hard cheeses' which are suitable for vegetarians.