Heat the butter. Add the onion, rosemary, salt, sugars, cinnamon stick and bay leaf and cook over medium meat for about a minute. Cover the pan, set the heat to low and cook for about 10 minutes until the onion pieces are very soft. Stir once in a while.
Stir in the rice wine and vinegar. Cover the pan once more. When the mixture is simmering, you can press the onion bits with the back of a spoon against the pan to help liquefy them. Simmer for five minutes.
Add the chili powder and balsamic. Stir. Turn off the heat. Cool the chutney. Fish out the cinnamon stick and bay leaf before serving.
If you want a smooth chutney, you can pulse it in the blender after it has cooled.