Mix whipping cream and sugar in a large microwave proof dish. Microwave for 13 minutes on high (for microwaves that are about 1100 watts) Add pecans, butter, and vanilla. Stir until mixture begins to cool and reaches the heat of crystallization. Drop by teaspoons onto wax paper. Cool before storing. If crystallization occurs too quickly, add 1 tablespoon of cream and mix well. Add additional tablespoons of cream as needed until all are dropped.