Place sugars, water and cream in a heavy, medium saucepan over moderate heat. Stir often and cook to a soft ball stage, about 8 to 10 minutes. Use a candy thermometer; the soft-ball stage is between 234 degrees F and 240 degrees F.

Remove from heat and beat mixture with an electric mixer in the pot on low setting until creamy, 2 or 3 minutes. Stir in all the pecans to coat evenly. Using a soup spoon or tablespoon, drop big spoonfuls of praline mixture onto a buttered sheet pan to cool.