Place the pecans on a baking sheet and toast in a 350°F (175°C) oven for 8-10 minutes or until fragrant. Allow them to cool.
Line your baking sheet for the pecan pralines with greased parchment paper or a silicone mat.
Combine the granulated sugar, brown sugar, cream, unsalted butter, and salt in a medium-sized saucepan.
Heat the saucepan over medium and bring the mixture to a gentle boil, stirring constantly.
Once it reaches a boil, insert a candy thermometer. Boil until the mixture reaches 235°F/115℃ (soft ball stage). It will foam and bubble slightly. Stir occasionally for even heating and to avoid burning.
Remove the saucepan from the heat. Let it sit for a few minutes to cool slightly and thicken, reaching about 200°F (95℃).
Add the pecan halves, chopped pecans, and vanilla extract (if using) to the saucepan. Stir them in with a wooden spoon to coat, and then do not stir again. Let the temperature come down to 150°F (65℃), then stir again for about a minute.
Drop spoonfuls of the pecan praline mixture onto a parchment-lined baking sheet with a spoon or cookie scoop. Allow the pralines to cool and set completely at room temperature, which takes 30 minutes to an hour.
Once the pecan pralines have completely set, remove them from the baking sheet. Store them in an airtight container at room temperature.