In a large bowl mix together the peanut butter, coconut oil, and agave nectar.
Set aside about 1/2 cup of the peanut butter mixture and add the cocoa powder to the larger bowl. Mix to combine.
Line a bread pan with parchment paper and pour the chocolate mixture into the pan. Drizzle the peanut butter mixture on top and use a toothpick or chopstick to swirl the peanut butter into the top of the fudge mixture.
Place in the freezer for at least 1 hour.
Slide a knife around the edges and pull the parchment paper to remove the fudge from the pan and cut into squares.
Sprinkle top with flaked sea salt, if desired and enjoy! Store in fridge.