In a large skillet over medium heat, cook the bacon, stirring occasionally, until crisp, about 15 minutes. Transfer to a strainer set over a bowl, separating the cooked bacon from the bacon fat. Set both aside. 

While the bacon is cooking, preheat the oven to 350F. 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 the bacon is cooking, in a small saucepan over medium heat, melt the butter. Set aside. 

Set aside 1/2 cup of the bacon. Brush another large, rimmed baking sheet with butter. Top with a sheet of phyllo and brush the phyllo with butter. Repeat, using 20 sheets of phyllo and about half of the butter. Spread about 2/3 of the Nutella on top, then sprinkle with the toasted nuts, cocoa nibs, and remaining bacon. Top with the remaining Nutella and set aside. 

Cover a work surface with a 12x16-inch piece of plastic wrap and brush it with butter. Top with a sheet of phyllo and brush the phyllo with butter. Repeat, using the remaining 20 sheets of phyllo and butter (you might not need all the butter). Pierce the phyllo stack all over with a fork, then use the plastic wrap to help lift the pierced phyllo stack off the work surface, placing the stack on top of the Nutella. Bake the 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 a boil. Set aside. 

When the baklava comes out of the oven, slowly and evenly pour the honey mixture over the top. Set aside for several hours to let the syrup soak in.