Heat the oil over medium heat in a medium stock pot. Add onion and bell pepper and sauté for 3 minutes.
Add ginger, garlic, and crushed red pepper flakes and cook for a minute. Add curry powder and salt and sauté for another minute. Add the diced mangoes, sugar, and vinegar and stir to combine.
Bring to a boil, then reduce heat and simmer for 40 minutes to 1 hour. Optional, Mash mixture with a potato masher if you like a smoother consistency. Remove from heat and allow to cool.
Yield: Makes a little more than 2 half pints.Make Ahead instructions: Mango Chutney can be made ahead of time and stored in an airtight container in the refrigerator for up to 2 weeks.Freezing Instructions: Store in a freezer safe container in the freezer for up to 6 months.To Can Chutney: Pour the hot mixture directly into sterilized jars. Top with new, cleaned lids and rings and process in a water bath for 10 minutes (or a longer if at high altitude). Allow to rest at room temperature on your counter for 24 hours, then store in a dark, cool place for up to one year.