In the bowl of a stand mixer, combine the oats, cocoa powder, flaxseed, chia seeds, salt, peanut butter, honey, and vanilla. Mix on low with the beater blade until well combined. Stop and scrape the sides of the bowl if necessary.
Stir in the mini chocolate chips.
Roll the mixture into small balls, about 1 to 2 tablespoons per ball. Place in an airtight container and keep refrigerated for up to 2 weeks.
If you don't have a stand mixer, you can use a bowl and wooden spoon to make the energy balls. You can also freeze the energy balls for up to 2 months. Keep in a freezer bag or container in the freezer.