Combine the stock, beans, peppercorns, garlic, 1 sprig rosemary, the bay leaf, carrots and onions in a large pot. Bring to a simmer and slowly cook until the beans are tender. Drain and reserve 3/4 cup of the liquid. Discard the rosemary, bay leaf and carrots.
Puree the beans, half the reserved liquid and the chestnuts in a food processor or blender until smooth, using additional liquid if necessary. Finish with the olive oil and some salt.
Heat a saucepan over medium heat. Add the guanciale and 2 tablespoons water. Cook slowly until the water evaporates, and then caramelize the guanciale. Remove the guanciale and reserve the fat. Add the pears to the pan and cook until tender, and then drain.
Brush the baguette slices with olive oil and toast. Assemble each bruschetta with a spoonful of the puree, caramelized guanciale and pears, and garnish with the remaining rosemary.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.