In a small bowl, mix the peanut butter, salt and powdered sugar until firm. Slowly melt the chocolate chips in a double boiler over hot, not boiling, water. You may also melt them in a microwave oven set on high for 2 minutes, stirring halfway through the heating time. Grease the muffin tin cups and spoon some chocolate into each cup, filling halfway. With a spoon, draw the chocolate up the edges of each cup until all sides are coated. Cool in the refrigerator until firm. Spread some of the peanut butter onto the chocolate in each cup, leaving room for the final chocolate layer. Cool the cups again to firm up the peanut butter. Pour some chocolate onto the top of each candy and spread it to the edges. Let sit at room temperature, or covered in the refrigerator. Turn out of the pan when firm.