1 (14 ounce) can sweetened condensed milk (not evaporated)
1 (12 ounce) package (2 cups) semisweet chocolate chips
1 teaspoon vanilla extract

Line 8-inch pan with foil so foil extends over sides of pan; butter foil. In 2 1/2 quart microwave safe bowl, combine condensed milk and chips. Microwave on HIGH for 1 1/2 to 1 1/4 minutes or until melted, stirring once during cooking. Stir until smooth. Add vanilla extract; stir well. Pour into buttered, foil-lined pan. Refrigerate until set.

Remove fudge from pan by lifting foil; remove foil from sides of fudge. Using large knife, cut fudge into squares. Store in airtight container in refrigerator.