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1
Begin the soup 2 days in advance.
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2
Rinse the kale and other greens and strip away the hard stems.
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3
Sprinkle the leaves generously with salt and drain in a colander in the sink for 30 minutes.
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4
Rinse and squeeze dry; then coarsely chop them.
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5
Meanwhile, heat half the olive oil in the 5-quart casserole over medium heat.
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6
If using earthenware, be sure to start on low and raise the heat gradually.
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7
Add the chopped yellow onions, celery, and carrot and cook until the vegetables are soft and just turning golden, about 20 minutes.
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8
Add the greens to the pot, stirring to coat them with oil.
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9
Crush half the cannellini beans to a puree.
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10
Add all the beans, the garlic, parsley, thyme, bay leaf, tomato sauce, and cheese rind to the mixture and cook, stirring, for a few minutes.
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11
Pour in 3 quarts warm water and slowly bring to a boil.
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12
Cover, reduce the heat, and simmer for 30 minutes to blend the flavors.
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13
Remove from the heat, uncover, and let cool.
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14
Stir the bread into the cool soup and return the pot to low heat.
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15
Raise the heat to medium-low and cook, stirring, until the bread crumbles and the soup turns creamy with small bread chunks here and there.
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16
Add water if necessary to keep the mixture smooth but always so thick a spoon can stand up in it.
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17
Let cool, cover, and refrigerate for 2 days.
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18
About 3 hours before serving, remove the soup from the refrigerator.
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19
Correct the seasoning with salt, plenty of black pepper, and a splash of vinegar.
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20
Remove the cheese rind (see Notes).
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21
Preheat the oven to 350F.
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22
Lightly oil the 12-inch-wide casserole and turn the ribollita into it.
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23
Top with slightly overlapping slices of red onion.
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24
Drizzle the remaining 1/3 cup olive oil over the top and bake for 2 hours.
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25
Turn off the heat and leave the dish in the oven until it cools down to warm, 35 minutes.
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26
Serve with a pepper mill and a cruet of your best Tuscan extra virgin olive oil.
