1. Cook bacon in a large nonstick skillet over medium heat until crisp. Remove bacon from pan; crumble. Increase heat to medium-high. Add butter and oil to drippings in pan; swirl to coat. Add onion; sauté for 5 minutes, stirring occasionally. Add garlic; sauté for 30 seconds, stirring constantly. Add flour, and sauté 1 minute, stirring frequently. Stir in mustard. Gradually add 1 cup milk, stirring constantly with a whisk, and bring to a boil. Cook for 3 minutes or until slightly thickened. Remove from heat. Let stand 5 minutes. Add cheese, salt, and pepper, stirring with a whisk until smooth.
2. Place pan over low heat. Stir in bacon, pasta, and peas; cook for 1 minute or until thoroughly heated, tossing to coat.