Preheat the oven to 350°F.
Spread the cubed sourdough in a single layer on a baking sheet. Drizzle with olive oil, season with salt and pepper, and bake for 15–20 minutes, until lightly toasted. Set bread aside.
Increase the oven temperature to 375°F. In a large skillet over medium-high heat, add olive oil, butter, and the bay leaf. Stir in onion, celery, apple, salt, pepper, rosemary, sage, and thyme. Cook 5–6 minutes, stirring frequently, until the vegetables and apple are crisp-tender.
Add the toasted sourdough cubes to the skillet and stir gently to combine. Slowly pour in the broth until all of the bread is softened. Remove the bay leaf. Adjust seasoning to taste.
Scoop the stuffing mixture into a prepared 12-cup muffin tin. Bake for 25–30 minutes, until lightly crisp on top. Serve warm or at room temperature.