First, blend the maple sugar in a high speed blender until powdered, about 40 seconds.
In a bowl, pour in the peanut butter, powdered sugar, salt, and vanilla extract. Use a spoon to stir until it is creamy and smooth.
Next, melt the chocolate chips in the microwave or on the stove. For the stove, heat a non-stick pan on low heat and pour in the chocolate chips. Stir constantly with a spatula until the chips are completely melted. For the microwave, pour the chocolate chips into a microwave safe bowl, cover, and heat for 20 second intervals, stirring in between each time. Heat until fully melted, about 1 minute and 20 seconds.
Then line a muffin tin with paper cups. Use a measuring tablespoon and fill half of it with the melted chocolate. Pour it into the cup, stirring it around until the bottom is fully coated with chocolate. Fill all of the cups.
Next, layer 1½ teaspoons of peanut butter on top of the melted chocolate. Use your fingers to gently press the peanut butter down. Fill all of the cups.
Finally, top each cup with ⅓ tablespoon of melted chocolate, completely covering over the peanut butter. Cover the tin with plastic wrap and chill it in the refrigerator for 1 hour or until fully set. Allow the peanut butter cups to thaw a few minutes before serving.