STRAWBERRY FILLING:

2 1/2 c. coarsely chopped hulled strawberries (about 1 1/3 pt.)
1/2 c. sugar
2 1/2 tbsp. cornstarch

COOKIE CRUST:

2 (5 1/2 oz.) pkg. shortbread cookies
3 tbsp. unsalted butter
2 tbsp. water
1 tsp. vanilla extract
2 oz. semi-sweet chocolate, chopped and melted

CHEESECAKE FILLING:

4 (8 oz.) pkg. cream cheese, at room temperature
1 1/2 c. sugar
4 lg. eggs, beaten
2 tsp. vanilla extract

SOUR CREAM TOPPING:

1 1/2 c. sour cream
3 tbsp. sugar
1 tsp. vanilla extract
2 oz. semi-sweet chocolate, chopped and melted

STRAWBERRY FILLING: Bring all ingredients to boil in small heavy saucepan, stirring constantly and crushing berries. Boil 2 minutes to thicken, stirring constantly (mixture will be slightly chunky). Pour into bowl and cool completely.

CRUST: Preheat oven to 350 degrees. Butter 9-inch springform pan. Blend cookies in processor until almost pasty, stopping occasionally to scrape down sides of bowl, about 3 minutes. With machine running, add butter, water and vanilla. Blend until mixture adheres to sides of work bowl. Press mixture firmly into bottom and 1 3/4 inches up sides of prepared springform pan. Refrigerate 15 minutes. Bake 10 minutes, transfer to rack and cool, reduce oven temperature to 325 degrees. Pour melted chocolate into bottom of crust. Spread with spoon.

CHEESECAKE FILLING: Beat cream cheese until smooth. Gradually add sugar and beat until fluffy. Add eggs and vanilla and beat until smooth. Ladle half of filling into crust. Place cheesecake on baking sheet. Bake until filling is barely set, top looks dry and filling moves in one piece when pan is shaken, about 35 minutes. Cool 20 minutes.

Gently spoon strawberry filling over cheese cake layer beginning at outer edge and ending in center to cover completely. Bake 15 minutes. Gently ladle remaining cheese cake filling over strawberry layer. Beginning at outer edge. Filling will be higher than crust sides. Bake until edges are set and center moves slightly when pan is shaken, about 50 minutes.

Meanwhile, prepare topping. Mix sour cream, sugar and vanilla in bowl. Cool cake 5 minutes. Maintain oven temperature. Spoon topping over cake. Bake 10 minutes. Transfer cheesecake to rack and cool. Run small sharp knife around top edge of cheesecake to loosen. Refrigerate overnight. Spoon melted chocolate into pastry bag and pipe over cheesecake in zigzag lines.