Cube bread and toast in a 350°F oven for 10-15 minutes. Set aside to cool. Alternately, spread on a sheet pan and leave on the counter overnight to dry out.
Meanwhile, in a large skillet, brown sausage over medium high heat. Cook for 6-8 minutes or until no pink remains, breaking up into smaller pieces. Remove from the pan and discard fat.
To the same skillet add butter, celery and onion. Cook over medium-high for 3 minutes or until softened and beginning to brown, scraping any brown bits from the bottom of the skillet. Add apple, garlic, sage, poultry seasoning, rosemary, salt and pepper. Cook for 3 minutes or just until apple begins to soften. Remove from heat.
In a large mixing bowl, whisk together broth, milk and eggs. Add cubed bread, sausage and vegetables. Mix well, adding more stock if needed, to fully moisten.
Spray 18 cups of two standard size muffin pans liberally with cooking spray. Divide mixture between cups.
Bake for 30-35 minutes or just until cooked through and the tops are crusty.
Let stand for 5 minutes, then serve.