Preheat oven to 325°. Spray an 8½×4½-inch cast-iron loaf pan with cooking spray. Line with parchment paper, letting excess extend over sides of pan.
In a small bowl, combine dates and hot coffee; let stand for 15 minutes.
In a medium bowl, whisk together flour, brown sugar, baking powder, cinnamon, salt, and baking soda.
In a large bowl, whisk together sour cream, oil, egg, whiskey, and vanilla; stir in dates and coffee.
Stir flour mixture into coffee mixture just until dry ingredients are moistened; stir in walnuts. Spread batter into prepared pan. Gently tap pan on counter 2 to 3 times to release any air bubbles. (Pan will be full but will not overflow in the oven).
Bake until top is golden brown and a wooden pick inserted in the center comes out clean, about 1 hour and 25 minutes. Let cool in pan on a wire rack for 10 minutes. Using excess parchment as handles, remove from pan, and let cool completely on a wire rack. Store in an airtight container for up to 3 days.
Notes
KITCHEN TIP-If you prefer to omit the whiskey, increase the vanilla extract to 1 tablespoon.
Recipe by Southern Cast Iron at https://southerncastiron.com/coffee-date-nut-bread/