1/4 c. cocoa
1 c. sugar
1/2 c. cornstarch
1/2 tsp. salt

Combine first 4 ingredients in a heavy saucepan. Gradually blend in milk, stirring constantly until filling boils. Boil for 1 minute. Remove from heat. Blend in butter and vanilla. Pour into two 9 inch pie shells. Carefully press plastic wrap onto pie filling. Chill 3-4 hours.