Answer: Some good herbs for windowsills are chives, bay tree, rosemary, thyme and basil. Some edible flowers you might manage on a windowsill are chives, lavenders and violas. You can also try dwarf citrus trees in tubs if you have space and light to suit them. These all require a good amount of bright light and if your growing area is a bit less than ideal you might want to start out with just a few smaller plants to experiment and see how it goes. You may find that you need to grow your plants under a flourescent light fixture fitted with bulbs that promote flowering -- full spectrum grow-lights are affordable, but the more expensive sodium halide lights will promote more flowering.
I am not sure which specific chocolate plant you are thinking of, but Cosmos atrosanguinea or Chocolate Cosmos apparently smells like chocolate to some people, vanilla to others. I don't think these are edible, though. There is a chocolate mint scented geranium available, too.
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