HEAT oven to 350°F. Melt 2 chocolate squares; set aside. Beat cream cheese, butter and granulated sugar in large bowl with mixer until blended. Add eggs and 1 tsp. vanilla; mix well. Mix flour, baking soda and salt. Add to cream cheese mixture; mix well. Blend in melted chocolate. Stir in cherries and nuts.
SPREAD into greased and floured 15x10x1-inch pan.
BAKE 25 to 30 min. or until toothpick inserted in center comes out clean. Melt remaining chocolate squares in medium microwaveable bowl. Stir in powdered sugar, 2 Tbsp. milk and remaining vanilla. Add remaining 1 Tbsp. milk, if necessary for desired glaze consistency. Drizzle over dessert. Cool completely.