PRALINE SAUCE: Heat 1 cup butter in large saucepan until melted. Add pecans and mix well. Bring to a boil. Cook until pecans begin to change color. (Mixture will foam over, so use a large saucepan.) Add remaining butter and mix well. This will cool the pecan mixture and stop the cooking process. Remove from heat. Combine brown sugar, whipping cream and cinnamon in a saucepan and mix well. Cook over low heat until blended, stirring constantly; increase heat. Cook to 230° F on a candy thermometer. Stir in pecan mixture. Add sour cream and vanilla and mix well. Remove from heat.