Cookie Dough Brownies

My mom found a recipe for this and made it then came across this one that was slightly different and declared that this one is the best one! I love this brownie!! It is so rich and decadent! I wanted to keep eating them! :) So amazingly delicious!!!! If you love cookie dough and you love brownies, you need to try these!!

1 cup butter
2 cups sugar
4 eggs
1 1/2 tsp vanilla
1/2 cup cocoa
1 1/3 cups flour
1/2 tsp salt
Filling:
1/2 cup butter, softened
1/2 cup packed brown sugar
1/4 cup sugar
2 Tbsp milk
1 tsp vanilla extract
1 cup flour
1/2 cup mini semi-sweet chocolate chips
Glaze:
2 cups milk chocolate chips
2 Tbsp shortening
3/4 cup walnuts (optional... I don't like nuts so I don't put these in)

Cream butter and sugar together. Add eggs and blend well. Add vanilla, salt, cocoa and flour. Don't over beat. Pour into greased 9x13 pan. Bake at 350 degrees for 20-25 minutes or until done. Cool completely.
For filling: IN a large bowl, cream butter and sugars until light and fluffy. Beat in milk and vanilla. Gradually beat in flour. Stir in mini chocolate chips. Spread over brownies (it works best to just press out with clean hands), then chill until firm.
For the glaze: in a microwave safe bowl, melt chocolate chips and shortening in 30 second intervals, stirring after each time, until smooth. Spread over filling. Immediately sprinkle with nuts, pressing down slightly.
Let glaze harden before cutting in.