Princess Tatiana of Greece really shows her passion for cooking. She released a cooking book and she posts her recipes on instagram. I remember years ago that I saw that she participated in some cooking event in Greece.
But then again, it all depends on their schedules. None of the working royals cook everyday because, well, they're royals, but because they don't have much time or patience. For them, cooking is rather a fun hobby. Rather, than necessity, unlike us, common folk, that have to cook on a daily basis or else we'll starve (talking healthy here, not grabbing pre-prepared food on the road like burgers).