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1
Preheat oven to 350u00b0F.
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2
To toast hazelnuts: spread on a baking sheet and bake for 15 minutes or until lightly browned and the skins begin to flake.
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3
Remove from oven and place nuts in a dish- towel.
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4
Roll up and let nuts 'steam' for 5 minutes and briskly rub the towel (with nuts inside) to remove the skins from the nuts.
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5
Cool and then chop coarsely.
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6
Set aside while you prepare dough.
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7
Reduce oven temperature to 300u00b0F.
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8
Line a large baking sheet (12 x 17) with parchment paper.
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9
In a food processor fitted with a metal blade, combine the coarsely chopped chocolate and brown sugar and process until the chocolate is very fine; set aside.
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10
Sift or whisk together the flour, cocoa, espresso powder, baking soda and salt into a bowl; set aside.
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11
In bowl of electric mixer combine the eggs and vanilla and beat to blend, about 30 seconds.
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12
On Low speed mix in the chocolate/sugar and flour mixtures until a stiff dough forms, adding the hazelnuts and white chocolate (if using) when about half mixed.
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13
On a floured surface divide the dough in half.
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14
Form each half into a log, 12 inches long.
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15
Do this by rolling the dough back forth into a cylinder shape with floured hands.
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16
Transfer the logs to the baking sheet, spacing then well apart (with-wise on the pan) Pat to even the shapes.
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17
Bake until firm to the touch about 40 minutes (logs will spread during baking).
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18
Remove from oven, place on wire rack, let cool for 10 minutes.
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19
Using a long spatula transfer the logs to a cutting board.
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20
With a serrated knife cut the dough into 3/4 inch thick slices on the diagonal.
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21
Arrange the slices on the baking sheet.
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22
Bake 20 minutes at 300u00b0F, turn the slices over and bake until crisp and dry, about 20 minutes longer.
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23
Let cool on wire rack.
