Toast the Pecans: Line a baking sheet with parchment paper. Preheat oven to 350°F. Spread pecan halves on sheet. Bake 7-10 minutes, flipping halfway. Pecans will begin to brown and become aromatic
Fasten the candy thermometer to the side of a large saucepan. Add the sugars, butter and milk. Stir consistently over medium high heat and bring the mixture to 235-240°F. *
Remove from the heat and mix in the pecans and vanilla. Store for about 2-3 minutes. The mixture will thicken as it cools. It will also lose some of its glossiness.
Use a cookie scoop to drop mixture onto the parchment paper.
Work fast as the mixture in the pot will set quickly.
Allow pralines to cool and solidify for a couple of minutes before serving.