Grease 9 inch spring form pan and dust with graham cracker crumbs. sieve cottage cheese into bowl, add soft cream cheese and beat on high speed until well blended and creamy.Beating at high speed add sugar, then eggs, Reduce to med speed and add corn starch, lemon and vanilla. Beat until well Blended. Add melted butter(or marg) and sour cream. Beat until smooth. Pour into Pan. Bake in 325 degree oven about 1 hour and 10 minutes. Or until firm around edges. Turn off oven and let cake stay in oven for 2 hours. Remove and cool completely on wire rake. Chill before removing side of pan.