In large skillet over medium heat, cook bacon, stirring occasionally, until crisped, about 15 minutes. Transfer to strainer set over bowl, separating the cooked bacon from the bacon fat. Set both aside.
While the bacon is cooking, preheat the oven to 350° F. Arrange the hazelnuts and walnuts on a rimmed baking sheet and bake until toasted and fragrant, about 10 minutes. Set aside to cool (leave the oven on).
Also while bacon is cooking, in small saucepan over medium heat, melt the butter. Set aside.
Set aside ½ cup of the bacon. Brush another large, rimmed baking sheet with butter. Top with sheet of phyllo and brush phyllo with melted butter. Repeat, using 20 sheets of phyllo and about half of the butter. Spread about ⅔ of the Nutella on top, and then sprinkle with the toasted nuts, cocoa nibs, and remaining bacon. Top with remaining Nutella and set aside.
Cover work surface with 12×16-inch piece of plastic wrap and brush it with butter. Top with sheet of phyllo and brush phyllo with butter. Repeat, using remaining 20 sheets of phyllo and butter (you might not need all the butter).
Pierce phyllo stack all over with a fork, then use plastic wrap to help lift pierced phyllo stack off work surface, placing stack on top of Nutella. Bake baklava until golden brown, 30 to 35 minutes.
Meanwhile, in a medium saucepan over medium heat, combine the honey, water, corn syrup and bacon fat and bring to boil. Set aside.
When baklava comes out of oven, slowly and evenly pour honey mixture over top. Set aside for several hours to let syrup soak in.
Cut into 20 pieces and serve garnished with remaining ½ cup bacon.