Step 1

Heat oven to 350°F. Let cookie dough stand at room temperature 10 minutes to soften.

Step 2

In large bowl, break up cookie dough. Add cocoa, food color and egg. Beat with electric mixer on medium speed 1 minute, scraping bowl frequently. Spread in bottom of ungreased 13x9-inch pan.

Step 3

Bake 25 to 30 minutes or until center is set. Cool completely in pan on cooling rack, about 1 hour.

Step 4

In 1-quart saucepan, mix flour and milk with whisk until smooth. Cook over medium heat 3 to 5 minutes, stirring constantly, until mixture is very thick. Remove from heat; cool 10 minutes.

Step 5

In large bowl, beat sugar and butter with electric mixer on medium speed 1 minute or until light and fluffy. Gradually add flour mixture by tablespoonfuls, beating on high speed until smooth. Beat in vanilla. Frost bars. Cut into 6 rows by 4 rows.