Preheat oven to 350°. Bake pecans in a single layer in a shallow pan 8 to 10 minutes or until toasted and fragrant.
Sprinkle sugar in an even layer in a small saucepan. Stir together syrup and 1/3 cup water, and pour over sugar in saucepan. Cook, without stirring, over medium-high heat 12 to 14 minutes or until sugar is dissolved and mixture is golden.
Remove from heat. Gradually whisk in evaporated milk. (Mixture will bubble.) Stir in butter and toasted pecans.