Boil 3/4 cup cream, sugar, corn syrup, and butter in a large saucepan over medium-high heat until mixture turns a rich brown color and temperature reaches 250 degrees, about 15 minutes.
Whisk in remaining 1/4 cup cream, vanilla, and salt. Remove from heat; cool 2 minutes.
Dip apples one at a time into hot caramel. Allow excess caramel to drip off, then quickly press nuts onto caramel layer before it cools. Refrigerate apples to set caramel. Serve apples at room temperature.