Melt butter in a frypan over medium heat; cook and stir the prosciutto, garlic and pine nuts in the melted butter until the garlic is fragrant and the nuts begin to turn brown, about 2 minutes. Stir in the lemon juice.
Bring a pot filled with lightly salted water to boil. Gently boil the asparagus until bright green and barely tender, about 3 minutes; drain. Add the asparagus to the prosciutto mixture and toss to mix evenly. Season with salt and pepper; serve hot.