Begin by lining an 8x8-inch square baking dish with parchment paper, allowing some overhang for easy removal later.
In a medium saucepan over low heat, combine the sugar-free dark chocolate chips, almond butter, and coconut oil. Stir continuously until melted and the mixture is smooth.
Remove the pan from heat and whisk in the unsweetened cocoa powder, powdered erythritol, vanilla extract, and salt until well combined.
If you're adding nuts, fold them into the mixture at this stage for an extra crunch.
Pour the chocolate fudge mixture into the prepared baking dish, spreading it evenly with a spatula.
Refrigerate the fudge for at least two hours, or until firm.
Once set, use the parchment paper to lift the fudge out of the dish. Cut it into squares and enjoy!