You'll need a large heavy saucepan (at least 2 quarts) with a lid and sturdy handle. Butter Sauce pan bottom and sides before adding ingredients. Make candy on a low humidity day.
Place the sugars, half and half and salt in your prepared sauce pan. Stir constantly over low heat until the sugars melt. Raise the heat to medium. Place the lid on the pan and let it heat for 3 to 5 minutes depending on how fast your stove heats. Remove the lid and once the syrup boils turn the heat down to simmer. Bring the syrup to 234 degrees. Remove from heat.
Add the butter and vanilla but don't stir. Let sit for 5 minutes. Add the chopped pecans. Stir with a wooden spoon until the candy loses it's gloss and thickens.
Spoon the candy onto buttered wax paper. Top each praline with a pecan half.