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1
Preheat oven to 350F.
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2
Butter and flour a 10-cup Bundt pan or tube pan.
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3
For the streusel filling:
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4
Mix together 3 tablespoons each flour, brown sugar and hazelnuts, 2 tablespoons espresso powder and melted butter in a small bowl until well blended.
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5
For the cake:
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6
Add whole wheat pastry flour, all-purpose flour, baking powder, salt and baking soda in a medium bowl, and whisk until well mixed.
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7
Pour the sour cream (or yogurt) and vanilla in a small bowl, and stir until well blended.
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8
Add butter, oil and sugar in a large mixing bowl with an electric mixer, beat on medium-high speed until well blended.
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9
Beat in eggs and egg whites, beating after each addition until just combined.
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10
Gradually add the dry ingredients into the wet ingredients, beat in low speed, scraping down the sides, until just incorporated, moistened and no dry spot is left.
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11
Spoon half the batter into the prepared pan and sprinkle evenly with the reserved coffee and nuts streusel filling.
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12
Scape the remaining batter over and smooth the top with a rubber spatula.
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13
Bake until a wooden stick inserted in the center comes out clean, about 1 hour.
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14
Let cool in the pan for 15 minutes on a wire rack, then remove from the pan and cool completely on the wire rack.
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15
For the glaze:
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16
Add powered sugar in a small bowl.
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17
Stir in coffee until smooth.
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18
Pour up to 1 tablespoon more of the liquid to thin the glaze to desired consistency if desired.
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19
Drizzle the glaze over the cooled cake.
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20
Sprinkle toasted hazelnuts.
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21
Serve or keep it cover and refrigerate until ready to use.
