Line an 8x8- or 9x9-inch baking pan with parchment paper, leaving an overhang on two sides like handles.
Place the peanut butter, honey, and coconut oil in a medium heatproof bowl. Set the bowl over a saucepan of water and bring the water to a simmer over medium to medium-high heat. (Do not let the water boil, and make sure the water does not touch the bottom of the mixing bowl.) Stir and heat until the mixture is smoothly combined. Remove the bowl from the saucepan and turn off the heat.
Add the oats, protein powder, flaxseed, cinnamon, and salt to the bowl with the peanut butter mixture. Stir to combine. The mixture will seem very dry at first but will come together as you stir. It won't be sticky but should hold together when pressed (see recipe notes for more details).
Fold in the chocolate chips. (If the mixture is still fairly warm, pop the bowl into the refrigerator for a few minutes to let it cool. Cooling the mixture will prevent the chocolate from melting. Don’t worry if they do melt a little—the bars will still be delicious!)
Press evenly into the prepared pan and refrigerate for 1 hour or until firm.
Lift the bars from the pan using the parchment handles and transfer them to a cutting board. Slice into bars as desired and enjoy.
Notes
TO STORE: Store the bars at room temperature for up to 1 week.
TO FREEZE: These homemade protein bars can be kept in the freezer for up to 3 months.
STORAGE TIP: I like to wrap mine individually, then remove them from the freezer as needed. You can also store them in the fridge, though I find they taste best at room temperature.
*INGREDIENT NOTE: The consistency of the bars will vary based on the brand of peanut butter you use. Add a tablespoon or two extra oats if they seem too loose. If they seem too dry, add additional peanut butter, honey, or even water, 1 tablespoon at a time, until the bars hold together easily when pressed into the pan.
**GLUTEN FREE: If you are particularly sensitive to gluten, I recommend sourcing oats (e.g., Bob's Red Mill) that are processed in a gluten free certified facility.
The nutritional information will vary based on the brand of protein powder you use. If you'd like to calc them with a specific brand, you can do so for free at myfitnesspal.com.