Date butter: Pulse butter and dates in a food processor, scraping down sides a few times, until smooth and combined. Date butter can be made up to a week ahead and stored in refrigerator; bring to room temperature before using.

Waffles: Whisk together flours, sugar, baking powder, baking soda, and salt in a large bowl. In a separate bowl, whisk together milk, sour cream, butter, eggs, and vanilla. Whisk milk mixture into flour mixture just to combine (do not overmix).

Preheat a waffle iron. Coat with a thin layer of cooking spray. Pour 1 1/4 cups batter per waffle into center of iron, allowing it to spread almost to edges. Close lid and cook until golden brown and crisp, 6 to 7 minutes. Remove from iron and quickly toss between your hands several times to release steam and help retain crispness, then transfer to a wire rack set in a rimmed baking sheet; keep warm in a 225 degrees oven until ready to serve. Repeat coating iron with more cooking spray between batches.

Serve, with date butter, fruit, pistachios, and syrup.