Line a medium-large bread pan with parchment paper, letting hang over sides and set aside.
In a large bowl, combine protein powder, flaxseed meal or almond meal and cacao powder. Stir until well mixed. Add nut/seed butter, melted coconut oil, and peppermint extract. Stir gently until well combined.
Begin adding one tablespoon of water at a time, until mixture forms into slightly crumbled dough texture. Dough should be moist, but slightly crumbly. Use your hands if necessary to make sure everything is well mixed at the end.
Press mixture into prepared pan with slightly wet hands. Flatten as much as you can. (I used the overhang of parchment paper to press and get really flat.)
Melt the chocolate: in a small microwave safe bowl, melt chocolate chips and coconut oil together on half power, about 20-30 seconds, in increments as needed, until chocolate is completely melted, then add in peppermint extract and stir again.
Pour melted chocolate over bars and place in freezer for 30 minutes, or refrigerator for at least 1 hour to set. Lift parchment paper from pan and cut into 10 bars.
Store bars in airtight container in fridge up to 2 weeks, and in freezer well wrapped for up to 3 months.