What Makes this dish truly good is the old bread soaked in milk, not only is it flavorful and mellow, but the traditions are steeped in preserving and respecting food; waste not want not. It makes for a great vegetarian main course. With some old bread and whatever was growing in the garden, the Italian immigrants could make a delicious meal.
4 cups day-old country bread cubes
1½ cups milk
3 medium zucchini
3 large celery ribs, peeled
2 red bell peppers
2 sweet onions, such as Vidalia or Walla Walla
1 cup finely chopped scallions (about 1 small bunch)
2 cups grated Grana Padano or Parmigiano-Reggiano
4 ounces provola, cut in small cubes
½ cup chopped fresh Italian parsley
1 tablespoon kosher salt
10 tablespoons extra-virgin olive oil
1. Preheat oven to 400 degrees F. Put bread in a bowl and pour milk over. Prepare vegetables for stuffing as follows. Halve zucchini crosswise, then lengthwise to make 12 pieces. Scoop out the centers to make “boats”. Finely chop the centers and put in a large bowl. Cut celery ribs into 4-inch lengths. Cut each bell pepper into 4 segments, at the natural breaks in the ribs, Remove seeds. Peel and halve onions crosswise, then cut each in half again to get 8 pieces in all. Remove inner pieces of onion to make onion boats. Chop the inner parts of the onions and reserve.
2. Squeeze excess milk from the soaked bread and put bread in the bowl with the chopped zucchini. Add the scallion, 1 cup grated cheese, the provola, the chopped parsley and 1 teaspoon of the salt. Mix well to combine.
3. Season vegetables with 1/4 cup olive oil and the remaining 2 teaspoons salt. Brush 2 large baking dishes with 3 tablespoons olive oil each. Scatter chopped onion in the bottom of the baking dishes. Stuff vegetables with the stuffing. Put the stuffed zucchini and peppers in one dish, the onions and celery in another. Sprinkle tops of vegetables with remaining 1 cup grated cheese. Cover baking dishes with foil and bake until vegetables release their juices and are almost tender, about 30 minutes. Uncover and bake until tender and the stuffing is browned and crispy, about 30 minutes more. (The peppers and zucchini may be done before the onions and celery, check them after 20 minutes). Serve warm or at room temperature.