Heat 1 1/2 cups coconut milk, sweetener and salt in a saucepan over medium-low heat. Combine remaining coconut milk and the 3 Tbsp cocoa powder, whisk, and add to the pan.
Pour 1/2 of the warm coconut milk mixture over the egg yolks (or substitute) and whisk (constantly if using real eggs).
Add the egg mixture to the warm coconut milk mixture in the saucepan, whisking constantly. Finally, add the remaining cocoa and whisk again.
Cook for 3 to 5 minutes over medium-low heat, stirring until the mixture coats the back of a spoon. Remove from heat and stir in the vanilla, coconut oil and stevia. Whisk until smooth and the fat has melted.
Briefly puree the mixture in a blender or process in food processor for a more silky texture, if desired.
Spoon into pie shell. Cool uncovered in the refrigerator or freezer until the top is firm.