You could use 12 tbls. cocoa plus 4 tbls. butter is substitue for chocolate squares.

1/2 Cup Butter 4 Squares unsweetened Chocolate 3 Cups Sugar 1/4 teas. salt 1-13 oz. can of Evaporated milk 1 teas. vanilla

Melt butter and chocolate over very low heat. Stir in sugar at about 3/4 cup at a time, being sure it is blended before making another addition. Mixture will become very thick and dry. Add salt and stir in milk gradually. Continue to cook 7-8 minutes to blend and dissolve sugar. Remove from heat and add vanilla. Serve hot or cold over ice cream and/or cake.