Step 1

Heat oil in a large saucepan over medium-high heat until shimmering. Add pancetta and cook until fat begins to render and pancetta is lightly browned, about 2 minutes. Stir in mushrooms, tossing until coated with oil. Cook, stirring, until mushrooms have browned and pancetta has rendered most of its fat, about 5 minutes longer. Stir in shallots and serrano and cook until softened, about 1 minute. Remove from heat and scrape pancetta mixture into a bowl. Set aside.

Step 2

Add stock to now-empty saucepan and bring to a boil over high heat. Add pasta. Cook pasta, stirring occasionally, for 2 minutes less than package instructions, then stir in greens. Cook for 1 minute longer, then stir in pancetta mixture, along with all the rendered fat. Cook until the pasta is al dente, greens are wilted, and liquid has mostly evaporated and formed an emulsified, creamy sauce, about 1 minute (if necessary, add water a tablespoon at a time if liquid completely evaporates before pasta is tender).

Step 3

Remove from heat and stir in lemon juice and extra-virgin olive oil. Season to taste with salt and pepper. Spoon onto plates and top with Parmesan cheese. Serve immediately.