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