How to Make It
Bring 3 quarts water to a boil in a Dutch oven.
Place torn bread in a food processor; process until coarse crumbs form. Melt butter in a large skillet over medium-high heat. Add 1 garlic clove to pan; sauté 1 minute. Add breadcrumbs; sauté 3 minutes or until golden brown and toasted. Remove breadcrumb mixture from pan; wipe pan clean with paper towels.
Add asparagus and peas to boiling water; cook for 3 minutes or until crisp-tender. Remove from pan with a slotted spoon. Rinse under cold water; drain.
Add pasta to boiling water; cook 10 minutes or until al dente. Drain and keep warm.
Heat olive oil in skillet over medium heat. Add onion and the remaining 2 garlic cloves; cook for 3 minutes or until tender, stirring frequently. Place flour in a small bowl; gradually whisk in chicken broth. Add broth mixture and milk to pan, stirring constantly with a whisk; bring to a boil. Reduce heat; cook 1 minute or until thickened. Remove from heat; add cheeses, salt, and pepper, stirring until cheeses melt. Add pasta, asparagus, and peas; toss well. Sprinkle with breadcrumbs and tarragon.