In a large bowl, stir together the oats, protein powder, flaxseed, cacao nibs, salt and espresso powder.
In a medium microwave safe bowl, combine peanut butter and coconut oil. Microwave for 30-60 seconds until melted. Add maple syrup and cocoa powder and stir to combine.
Using a rubber spatula, pour the wet ingredients into the dry ingredients and stir until the dry ingredients are evenly coated.
Line a 9x9 baking pan with a silicone mat, parchment paper or wax paper and pour the mixture into it. Press the mixture firmly into the pan (tip: wet your hands slightly to prevent sticking) and place in the freezer for at least 30 minutes or the refrigerator for 1 hour.
Remove the pan from the freezer and using the lining, pull the bars out and place on a cutting board. Cut into 16 bars and enjoy.
Notes
LeftoversStore leftover bars at room temperature for up to 3 days, in the refrigerator for up to a week or freeze for up to 3 months. Enjoy straight from the freezer or allow to come to room temperature.**While the bars can be kept at room temperature, they are definitely quite soft. For best texture, I recommend keeping them in the fridge or freezer.