Preheat oven to 350°.
Prepare brownie mix according to package directions. Spoon batter in 9-inch springform pan.
Bake 20 minutes. Cool and reduce oven temperature to 325°.
In large bowl, beat cream cheese until fluffy. Gradually beat in milk. Add melted peanut butter, chips, eggs and vanilla; mix well.
Pour filling over baked brownie. Place pan in a large baking pan with 1-inch hot water (keeps brownie from overbaking).
Bake 50 to 55 minutes or until center is almost set.
Turn oven off; remove baking pan with water. Let cheesecake cool in oven 30 minutes.
Remove cheesecake from oven; chill 1 hour.
Remove side from springform pan.
In small saucepan, melt chocolate chips with shortening; stir until smooth.
Spread chocolate glaze over top and sides of cheesecake. Chill 3 hours. Garnish as desired.