Heat oven to 325ºF. In medium bowl, stir together all crust ingredients. Press into bottom (and 1 inch up the sides) of a 9-inch springform pan. Wrap pan with heavy-duty foil; freeze 30 minutes.
In large bowl, beat cream cheese, sugar and vanilla at medium speed until blended. Beat in sour cream and 1 cup cream. Add eggs one at a time, beating just until blended.
Slowly beat in flour, then gently fold in brownies.
Place springform pan in large baking or broiler pan. Pour batter into crust (batter will come to within 1/4 inch of top edge). Add enough hot tap water to baking pan to come halfway up sides of springform pan. Bake 1 hour 15 minutes to 1 hour 30 minutes or until edges are puffed and top is dry to the touch. Center should move slightly when pan is tapped, but should not ripple as if liquid. Remove springform pan from baking pan; remove foil. Cool completely on wire rack. Refrigerate overnight.
Melt milk chocolate and 1/3 cup cream in medium saucepan over low heat, stirring until smooth. Pour over top of cheesecake; let stand 10 minutes.
Pour white chocolate into small resealable plastic bag; snip off corner of bag. Drizzle chocolate over cheesecake. Refrigerate at least 1 hour. Refrigerate leftovers.