Potted Pork Tenderloin with Sweet Onions and Apple

Name: Potted Pork Tenderloin with Sweet Onions and Apple
Ingredients: 2 pork tenderloins, well-trimmed and cut into large chunks (about 2 1/2 pounds); 1 1/2 teaspoons ground fennel or fennel pollen; Kosher salt and freshly ground black pepper; Flour, for dredging; 2 to 3 tablespoons extra-virgin olive oil; 3 tablespoons butter; 4 medium onions, cut into thin wedges, root end attached; 2 medium Macintosh apples, peeled and chopped; 2 fresh bay leaves; A few sprigs fresh sage, very thinly sliced; 1/4 cup calvados; 1 cup chicken stock or cloudy apple cider