How to Make It
In a large deep frying pan, cook the bacon over moderate heat until crisp. Remove the bacon with a slotted spoon. Pour off all the fat from the pan.
In the same pan, heat the oil over moderately low heat. Add the garlic, red-pepper flakes, and anchovy paste and cook, stirring, until fragrant, about 30 seconds. Stir in the escarole, a little at a time, until wilted, about 3 minutes. Add the broth and 1/4 teaspoon of the salt and bring to a simmer. Reduce the heat and cook, covered, for 5 minutes.
Meanwhile, in a large pot of boiling, salted water, cook the spaghetti until just done, about 12 minutes. Drain the pasta; add it to the pan with the escarole. Stir in the remaining 1/4 teaspoon salt, the Parmesan, bacon, and butter.
Stir in a cup of drained canned cannellini beans when you add the broth in Step 2.
Add two tablespoons of chopped fresh basil just before serving.