Preheat oven to 325°. Spray a Bundt pan with cooking-oil spray. In a large bowl, combine pastry flour, all-purpose flour, granulated sugar, baking powder, baking soda, and salt. Stir in 1 cup brown sugar.
In a blender, whirl cocoa and dates with 2/3 cup boiling water until smooth. Whirl in buttermilk, eggs, oil, and vanilla. Set aside.
Put bittersweet chocolate in a small glass bowl and microwave on high for 10 seconds. Stir and repeat until melted. Stir 1/2 of date mixture into flour mixture. Stir in melted chocolate, then remaining date mixture, and finally chocolate chips.
Pour batter into prepared pan and bake until a toothpick inserted in the center comes out clean, about 40 minutes. Cool cake 15 minutes, then gently remove from pan and cool completely on a wire rack.
In a small saucepan over medium heat, melt butter, espresso powder, and remaining 1/4 cup brown sugar. Add cream and simmer 1 minute. Remove from heat and stir in powdered sugar until smooth. Stir in Bourbon and let cool. When glaze and cake are both at room temperature, drizzle glaze over cake.