1. Bring a large pot of water to a boil. Fill a large bowl with iced water.
2. Score an X into the bottom of each peach.
3. Drop the peaches into the boiling water for 10-15 seconds and then transfer to the iced water. Remove from the ice water after a minute or so and transfer to a cutting board.
4. Once cool enough to handle, remove the pits from the peaches and roughly chop.
5. Add the olive oil to a medium sized saucepan over medium heat. Saute the onions and jalapeno until soft, about 10 minutes.
6. Add the peaches and remaining ingredients to the saucepan. Reduce the heat to low and stir until combined. Cook for 30-45 minutes.
7. Use a potato masher to mash the ingredients into a thick sauce. Serve warm.