Pasta Primavera with Crispy Onion Gremolata

Name: Pasta Primavera with Crispy Onion Gremolata
Ingredients: 3 spring onions, bulbs and stems separated, thinly sliced; ½ cup vegetable oil; Kosher salt; 3 tablespoons chopped fresh chives; 1 tablespoon plus 1 teaspoon finely grated lemon zest; 1 cup shelled fresh fava beans (from about 1 pound pods) or frozen fava beans, thawed; ½ bunch asparagus, sliced into ¼-thick pieces; 12 ounces linguine; 2 garlic cloves, finely chopped; 6 ounces morel or crimini mushrooms, halved if large; 1 cup crème fraîche; 1 tablespoon fresh lemon juice; Freshly ground black pepper