Line a standard 12-cup mini muffin tin with paper liners.
Melt the chocolate chips using a double boiler or in the microwave (put in a microwave-safe proof bowl and heat at medium heat for 1 minute. Stir, then continue to heat using 30 seconds intervals, until chocolate is almost completely melted). Be careful not to overheat the chocolate because it will burn.
Using a teaspoon measuring spoon, add 1 to 1 1/2 teaspoons of melted chocolate into each muffin cup and use the spoon to lightly coat the sides of the liner. Freeze for about 5 minutes to harden.
In the meantime, reheat the remaining chocolate for the topping. Remove pan from the freezer and place a small spoonful of the peanut butter into each chocolate cup. Top each with a layer of the melted chocolate, then sprinkle with the chopped nuts. Can leave out at room temperature or freeze again for 5 minutes to harden the chocolate.
Repeat process with remaining chocolate and peanut butter. Store at room temperature for up 2 days or in the refrigerator for up to 1 week.
*For food allergies: substitute almond butter or SunButter (sunflower seed butter) for the peanut butter in the cups. Prepare the filling the same way by draining the excess liquid off the top of each butter.