Line an 8x5" loaf pan with parchment paper both ways, set aside.
In a large mixing bowl, stir together the honey, hazelnut butter, vanilla paste, stevia extract and salt with a rubber spatula.
Dump in the protein powder and cocoa powder and stir together. It will get really thick, but that's normal! You're just cooking AND getting an arm workout ;)
Once the fudge "dough" is nice and even, scoop the mixture into the prepared loaf pan and flatten it out with the rubber spatula. Cover and refrigerate overnight.
The next day, slice the fudge with a sharp knife (I sliced mine into 8 rows down the 8" side of the pan, and 4 rows down the 5" side of the pan). Since the fudge is slightly sticky, store the fudge on a sheet of parchment paper on top of a tray, about 1" apart from each other. Store covered in the fridge.