Put the butter and garlic in a stock pot on medium heat. Chop the onions and add. After 5 min add finely chopped potatoes and green chilis. Once the potatoes and onions have sweated and started to soften, add the chicken broth and balsamic vinegar. Bring to a hard boil and simmer 10 minutes. Add tomatoes and chili paste. (I like more chili paste than my wife because it's quite spicy, so I keep that out as a condiment)
Add the whipping cream right before serving so that you can store the left overs more easily.