Nasturtium flowers are easy to grow here in the Midwest, USA. They really are effortless, provide nectar and pollen for bees and butterflies, and both leaves and flowers are edible. I find there is no need to spray them either, so they are totally organic and pesticide free.
Here are a couple ideas. The first is just as a garnish for almost anything. Here with vanilla ice cream. I've also put them on cakes, salads, and omelettes.
Here is a video of me making the top dish of Nasturtium Dolmas found on the On Vegetables cook book by Jeremy Fox.