Rinse the beans under cold running water..
Place the beans in a large bowl, add enough cold water to cover by about 2 inches.
Let stand at room temperature overnight.
In a large Dutch oven (or heavy duty pot), combine the drained beans, the stock, and 1/2 cup of the olive oil
Add enough cold water to cover the beans by about 1 1/2 inches.
Add the onions, carrots, whole garlic cloves and sage.
Bring to a boil, and then reduce to low, partially cover.
Simmer until the beans are very tender, about 2 hours.
Remove the onions, garlic cloves, and sage. Discard.
About 30 minutes before the beans are done, in a large skillet, heat the oil over medium-high heat.
Add 2 tablespoons of olive oil.
Add the minced garlic, red pepper flakes, and pancetta. Saute for about 1 minute.
Add the escarole and saute until the leaves begin to wilt, about 3 minutes.
Add the tomatoes, 1 teaspoon of salt, and 1/2 teaspoon of black pepper, and cook, stirring occasionally, until the leaves have softened and the mixture is reduced to about 1/3 - about 8 minutes.
When the beans are finished, add the escarole mixture and stir.
Break up some of the beans with the back of a wooden spoon, to thicken slightly.
Stir in the lemon juice.
Season liberally with salt and pepper (taste as you add).
Serve immediately, passing the olive oil.