Combine sweetened condensed milk, whole milk, evaporated milk, cream, sugar, molasses, and vanilla extract together using a whisk in a large bowl, taking care to avoid creating bubbly foam. Refrigerate mixture for 30 minutes.
Preheat oven to 350 degrees F (175 degrees C).
Melt butter in a large saucepan over medium-low heat; stir in salt until dissolved. Mix pecans into melted butter until evenly coated. Spread coated pecans in a single layer onto a baking sheet.
Bake in the preheated oven for 6 minutes. Flip pecans and continue baking until toasted and fragrant, about 6 minutes more. Remove butter pecans from oven and coarsely chop. Measure 1 1/2 cups butter pecans and reserve the remaining for another use.
Pour cream mixture into an ice cream maker and follow manufacturer's instructions for ice cream. When ice cream is semi-solid (about 30 minutes), stop the machine. Pour ice cream into an air-tight container and fold in 1 1/2 cup butter pecans. Cover ice cream with plastic wrap and seal container with a lid. Freeze ice cream until solid, at least 2 hours.
Substitute 3 cups whole milk for the 2 cups whole milk and 1 cup heavy whipping cream, if desired. I generally use the 3 cups whole milk version. (for cost cutting) However, the whipping cream version will create a smoother texture.
Unused buttered pecans can be frozen for future batches of ice cream, if you can resist eating them as snacks.
Reason for chilling mixture and covering with plastic wrap is to prevent ice crystals from forming in your ice cream.
Nutrition data for this recipe includes the full amount of butter pecans. The actual amount of butter pecans consumed will vary.