How to Make It
Smash 3 garlic cloves. Place scallions, cream, and smashed garlic in a small saucepan. Finely chop remaining 3 garlic cloves to equal 1 tablespoon; set aside.
Bring scallion mixture to a boil over medium-low. Reduce heat to low; simmer, stirring occasionally, until scallions are crisp-tender and garlic is softened, about 10 minutes. Pour mixture into a blender. Secure lid; remove center piece to allow steam to escape. Place a clean towel over opening. Process until smooth, about 40 seconds. Stir in salt; set aside.
Cook pasta in a pot according to master technique (until very al dente, 3 minutes less than package directions call for).
While pasta cooks, melt 2 tablespoons butter in a large skillet over medium. Add reserved 1 tablespoon chopped garlic; cook, stirring often, until softened and fragrant, about 1 minute and 30 seconds.
Using a spider, transfer pasta to skillet, reserving cooking liquid. Add scallion-cream mixture and peas to skillet; increase heat to medium-high. Add 1/4 cup reserved cooking liquid; cook, stirring and shaking skillet constantly, until pasta is tender and sauce is loose and creamy, about 2 minutes. Remove from heat; add speck, cheese, mint, lemon zest and juice, remaining 2 tablespoons butter, and 1/4 cup cooking liquid, stirring until combined.