1. Position a rack in the centre of the oven and preheat to 350F (180C)
2. Butter and flour (or use veggie spray) a 9 inch springform pan.
3. Arrange the walnuts in a single layer on a baking sheet. Toast in the oven until light brown and fragrant, about 10 minutes. Let the nuts cool while you prepare the rest of the cake.
4. Peel, core and chop the pears into 1/2 inch pieces.
5. Whisk the flour, baking powder and salt together in a small bowl.
6. In the bowl of a stand mixer fitted with the paddle attachment, or in a large bowl, combine the chestnuts and sugar. Mix on low speed until the chestnuts have broken up into a coarse meal.
7. Add the butter, turn the mixer up to medium high and cream the mixture till light and fluffy, about 5 minutes.
8. Add the eggs one at a time, mixing for 30 seconds and scraping down the bowl in between each addition. Add the vanilla extract.'
9. Use a rubber spatula to fold in the flour mixture until just combined.
10. Then fold in the pears, walnuts and cocoa nibs. The batter will be thick. Spoon the batter into the prepared pan, and spread it out evenly, smoothing the top with an offset spatula.
11. Tap the pan gently on the counter to help the batter settle into the pan.
12. Bake until a toothpick or skewer inserted into the middle of the cake comes out clean and the edges are golden brown, between 50-60 minutes. Check at 50 for sure, since each oven is different (Yossy says it should take between 40-50 minutes. It has always been underdone at 40 minutes for me though)
13. Let the cake cool in the pan placed on a cooling rack. Let cool 45-60 minutes before removing the sides of the pan. Once cooled completely, you can take care of the top.

Cocoa and Sugar Dusting Top

1. Combine the black cocoa powder and icing sugar in a small bowl till completely blended. Using a small strainer, dust the entire top of the cake with this mixture.

Ganache Top

1. Chop the chocolate into small pieces and place into a small bowl.
2. Heat the cream over medium heat till warmed through and simmering.
3. Pour the cream over the chocolate and cover the bowl. Let sit for 5 minutes.
4. Stir the mixture through until completely blended.
5. Once cooled but still pourable, transfer the ganache to a small sandwich bag. Seal the bag. Using scissors, trim away a small section from one of the bottom corners.
6. Hold the bag in your hand, with the corner down, and squeeze gently until the ganache starts to drizzle out. Using a freehand motion, drizzle the ganache all over the surface of the cake (have the cake sitting on the cooling rack set over a wax paper lined baking sheet) Once you are happy with the design, you are done! Let it cool and set up before slicing.
7. Leftovers can be stored in an airtight container for a good two days.