Preheat oven to 350~. Place butter in 9" square pan in the oven until butter melts. Combine crumbs with gelatin and sugar. Remove 1/4 c crumbs to use as garnish. Stir remaining crumb mixture into the melted butter in the pan, patting mixture evenly over bottom of pan. Bake exactly 8 minutes. Mix until light and fluffy cream cheese and sour cream. Beat in butter, corn starch, eggs, sugar and vanilla. As soon as crust is baked, put out oven rack without removing pan and pour filling directly over hot crust. Sprinkle top with reserved crumb mixture and return to bake at 350~ for 30 to 35 minutes or until knife inserted comes out clean. DO NOT OVERBAKE. Let cool 30 minutes before cutting.