Melt the butter in a large, deep skillet. Add the pancetta and cook over moderately high heat, stirring, until just beginning to brown, about 5 minutes. Add the garlic and jalapeño and cook until fragrant, about 30 seconds. Add the peas and toss to coat. Add the pasta along with the reserved pasta water and the cheese. Season generously with pepper and cook over moderately high heat until the sauce is thick and creamy, about 2 minutes. Stir in the chives, parsley and mint and serve right away.