In a medium bowl melt the chocolate and the butter or oil in the microwave. I melt chocolate in the microwave stirring every 30 seconds. You can do this on the stove top over low heat if you prefer.
Stir in the peanut butter, vanilla, and sweetener.
In a large bowl mix the nuts and coconut. Pour the chocolate mixture over the nuts and coconut. Stir well. Spread onto a large baking sheet lined with waxed paper or parchment paper. Sprinkle half the topping over the trail mix.
Refrigerate until firm. Sprinkle the rest of the topping over the trail mix and mix well. Break up any large pieces. Store in the fridge.