Heat 2 tablespoons butter in nonstick saucepan over low heat. Add onion and garlic; cook, stirring, 7 minutes, until softened, making sure garlic doesnt burn. Add mushrooms; cook 3 minutes.
Simmer cream in clean medium-size saucepan 4 minutes. Add remaining 2 tablespoons butter, salt, pepper, chives and basil; cook 2 minutes.
Meanwhile, cook capellini in large pot lightly salted boiling water until al dente, firm but tender. For last 5 minutes of cooking, add carrots, broccoli and asparagus. For last 2 minutes of cooking, add squash, zucchini and peas. All vegetables should be tender at end. Drain well.
Return pasta with vegetables to pot. Add butter-cream sauce and Parmesan; stir over low heat 2 minutes. Makes 6 servings.