Whisk chicken stock, egg yolk, cornmeal, kosher salt, and white pepper together in a saucepan. Bring to a low boil; cook and stir until cornmeal absorbs all the chicken stock, about 8 minutes. Remove polenta from heat and cool.
Preheat oven to 325 degrees F (165 degrees C). Spray a casserole dish with cooking spray.
Cook and stir sausage, onion, fennel, and garlic in a large nonstick skillet over medium heat until sausage is fully cooked and vegetables are tender, about 15 minutes. Stir sausage mixture into polenta until fully incorporated. Add bread cubes, pears, parsley, balsamic vinegar, sage, summer savory, and nutmeg; stir to combine. Transfer polenta mixture to the prepared casserole dish; cover with an oven-proof lid or aluminum foil.
Bake in the preheated oven until polenta dressing is cooked through and slightly browned on top, 30 to 35 minutes.
