Line an 8×8-inch square baking pan with parchment paper. I like to use binder clips to clamp the parchment down so it stays in place.
Combine oats, peanuts, chocolate chunks and chia seeds in a large mixing bowl.
Heat peanut butter and maple syrup in a medium saucepan over medium low heat, stirring constantly until combined and warm, about 2-3 minutes. Remove from heat and stir in vanilla and sea salt.
Pour peanut butter mixture into the bowl with the oat mixture and stir until everything is evenly coated. It’s okay if the chocolate starts to melt.
Dump mixture into your prepared pan and press the mixture down firmly using your hands or a rubber spatula so it’s evenly spread out. Sprinkle more chocolate chips on top and press them down into the bars.
Once bars are pressed down firmly, place bars in the fridge for at least 2 hours to allow them to cool and firm up.
Once the bars feel solid/hard to the touch, remove them from the pan, place on a cutting board and slice into 10 even bars. Serve immediately or save for later.
These bars will stay together best if you store them in the refrigerator. They will keep for 1 week in an airtight container in the fridge. For freezing, wrap them individually and store in the freezer for up to 2 months.