1. Heat oven to 350. Cook the chopped pecans on a pan for 8-10 minutes until they are toasted and fragrant.
2. In a saucepan bring the brown sugar, whipping cream, and butter to a boil over med-high heat. Stir constantly. Boil for 1 full minutes.
3. Remove from heat, whisk in the powdered sugar and vanilla until smooth.
4. Fold in pecans. Let it cool until it's thickened.
5. Line the baking sheet with wax paper.
6. Spoon into 12 large or 24 small lumps. Let it cool at least 30 minutes. They should be holding their shape and firm to the touch before you remove them.