Heat oil in electric pressure cooker on Saute medium. Add onion; cook 5 to 7 minutes or until golden brown. Add 1 teaspoon salt; cook and stir 1 minute. Add pasta, sausage and 5 cups water; mix well. Cover and cook on Manual/High 5 minutes.
Meanwhile, melt 2 tablespoons butter in medium skillet over medium-high heat. Add garlic; cook and stir 30 seconds. Add panko and remaining ½ teaspoon salt; cook and stir 2 minutes or until panko is golden brown.
Use quick release to release pressure. Remove lid and turn pot to Saute. Add cheeses, milk and remaining 2 tablespoons butter; cook until cheeses are melted and mixture is smooth. Turn off pressure cooker. Let stand, uncovered, 5 to 10 minutes or until sauce is thickened and absorbed, stirring occasionally. Top with panko mixture.
