Sprinkle 1/2 cup pecans evenly over the bottom of each of 2 greased and floured 9-inch springform pans.
Microwave chocolate squares in a microwave-safe bowl at MEDIUM (50% power) 1 1/2 minutes, stirring at 30-second intervals until melted. Stir until smooth.
Beat butter and 2 cups sugar at medium speed with an electric mixer until light and fluffy. Add 4 eggs, 1 at a time, beating just until blended after each addition. Add melted chocolate, beating just until blended.
Add flour, beating at low speed just until blended. Stir in 1 teaspoon vanilla and chocolate morsels. Divide batter evenly between pans, spreading over chopped pecans.
Beat cream cheese at medium speed with an electric mixer until smooth; add 1 3/4 cups sugar, beating until blended. Add 7 eggs, 1 at a time, beating just until blended after each addition. Stir in 2 teaspoons vanilla. Divide cream cheese mixture evenly between each pan, spreading over brownie batter.
Bake at 325° for 1 hour and 15 minutes or until set. Remove from oven; cool completely on wire racks.
Spread top of each cooled cheesecake with 1 recipe Chocolate Glaze; cover and chill 8 hours. Remove sides of pans before serving. Garnish, if desired.