Line a baking sheet or flat surface with parchment paper.
Lay the pecans on a rimmed baking sheet and bake at 375 for 7 minutes or until they start to release their oils. Pull from oven and toss with about a teaspoon of butter and a sprinkling of salt. Set aside to cool completely.
In a heavy 3 quart saucepan (preferably nonstick), combine both sugars and corn syrup. Put the pan over medium, insert the candy thermometer and heat until mixture reaches 250 degrees F. This should take about 10-15 minutes, and you shouldn’t really need to stir much. Keep the heat rising slowly and steady.
Remove from heat and stir in butter, one chunk at a time until melted. Pour in the cream, then return the pan to heat, stirring constantly and keeping the candy at a slow boil/rapid simmer, until mixture reaches 242 degrees F. This should take about 15 minutes. It’s important to go slow and keep the mixture moving just enough not to burn. If temperature stalls, raise it in tiny increments.
Remove from heat and add pecans, vanilla and salt, then stir with a wooden spoon allowing the mixture to cool and thicken just slightly. Drop by spoonfuls onto the parchment lined paper and let set. Note: You don’t have to work as quickly with chewy pralines because it takes longer for them to set. In fact, if the first one you spoon out runs just stir a bit and let the mixture cool and thicken a little before spooning out the next one.