In 9 inch microwave dish, melt butter for 30-45 seconds on High power (100%) until melted. Stir in crumb mixture, and press into dish to form crust on bottom of dish. Set aside.

Soften cream cheese for 30 seconds to 1 minute at 70% power, or until quite soft. Beat until creamy. Add 2/3 cup sugar. Mix in eggs, one at a time. Blend in sour cream and vanilla.
Pour half or more of mixture into crust.

Mix cocoa and remaining 2 tablespoon sugar. Add to remaining vanilla mixture along with Amaretto. Mix well and pour over vanilla filling. Swirl chocolate mixture through vanilla mixture. 

Microwave on Medium power (50%) for 15-18 minutes, or until center is set. Cool and refrigerate until cold and firm before serving.