Heat olive oil in large skillet over medium heat. Add pancetta and cook 5 minutes, stirring frequently, until golden and crispy. Transfer to bowl with slotted spoon, leaving rendered fat in pan.
Add 2 tablespoons butter to same skillet. Add shallots with pinch of salt and cook on low heat 5 minutes until soft and golden. Add garlic and cook 1 minute until fragrant.
Add frozen peas to skillet and cook 5 minutes on medium-high heat until tender.
Add heavy cream, nutmeg, and black pepper. Bring to gentle simmer and cook 3 minutes. Remove from heat.
Meanwhile, bring large pot of salted water to boil. Cook pasta 2 minutes less than package directions. Reserve 1/2 cup pasta water before draining.
Return drained pasta to pot over medium-high heat. Add remaining 3 tablespoons butter and reserved pasta water.
Add pea mixture and crispy pancetta. Toss continuously for 1 minute until pasta is coated and creamy.
Serve immediately with grated Parmesan cheese and extra black pepper.