Heat the oven to 325ºF with a rack in the middle position. Lightly coat a 12-cup nonstick Bundt pan with butter and flour. In a medium saucepan over medium-high heat, bring the dates and coffee to a boil. Remove from the heat and let sit for 15 minutes. In a large bowl, whisk together both flours, the baking powder, salt and baking soda.

Transfer the coffee-date mixture to a food processor, add the sugar and process until smooth, about 1 minute. Add the eggs, vanilla and allspice. Then, with the processor running, add the butter. Pour the date mixture over the flour mixture and whisk gently until thoroughly combined.

Transfer to the prepared pan, cover tightly with foil and bake until firm and a toothpick inserted at the center comes out clean, 55 to 65 minutes. Remove the foil and cool in the pan on a rack for 15 minutes.

While the cake cools, in a medium saucepan over medium-high heat, combine the sugar, corn syrup, zest and salt. Bring to a boil, then cook until the mixture hits 240ºF, 2 to 3 minutes. Reduce to low and add the whiskey, 2 tablespoons at a time, allowing the bubbling to subside before adding more. Whisk in the butter 2 tablespoons at a time until melted and smooth.

Invert the cake onto a serving platter. Brush the top and sides generously with the warm toffee sauce. Slice and serve drizzled with additional sauce. The sauced, cooled cake can be wrapped tightly in plastic wrap and kept at room temperature for up to 3 days. Cooled sauce can be refrigerated for up to 1 week. To reheat, wrap the cake in foil and place in a 300ºF oven until warmed. Microwave the sauce until bubbling.