Cut the baguette into small cubes and spread them in a single layer on a baking sheet. Bake at 325°F for 10-15 minutes, tossing halfway through, until the cubes are dry and lightly crisp but not browned. Let cool.
Finely chop the fresh parsley, thyme, sage, rosemary, and dried cranberries. Set aside.
Melt the butter in a skillet over medium heat. Add the onion and celery and sauté for about 5-7 minutes, until softened. Add the crushed garlic and sauté for another 30-60 seconds, until fragrant.
Place the dried bread cubes in a large mixing bowl. Add the cooked onion, celery, and garlic, along with the chopped parsley, thyme, sage, rosemary, salt, pepper, and dried cranberries. Toss gently to combine.
Pour the whisked egg and chicken broth over the bread mixture. Toss gently until everything is evenly moistened. Let the mixture sit for a few minutes so the bread can absorb the liquid. Add more broth, one tablespoon at a time, if needed. The bread should be moist throughout but not soggy.
Spray a 12-cup non-stick muffin pan with oil. Use a large ice cream scoop to divide the stuffing mixture evenly among the muffin cups. Gently press the mixture into each cup so the muffins hold together.
Bake at 375°F for 18-22 minutes, or until the tops are golden brown and crispy and the centers are cooked through.
Let the stuffing muffins rest in the pan for 5 minutes before carefully removing. Serve them warm and enjoy!