Line 24 mini muffin cups with petit four paper cups. In 1-quart saucepan, melt semisweet chocolate chips over low heat, stirring frequently. Spoon about 2 teaspoons of the chocolate into each paper cup. With back of small measuring spoon, spread chocolate up sides to within 1/8 inch of the top. Chocolate should be warm enough to spread. Refrigerate about 20 minutes or until completely set.