Ham and Hash Brown Breakfast Bake

Name: Ham and Hash Brown Breakfast Bake
Ingredients: 8 slices bacon; 3/4 cup chopped sweet onion; 1/3 cup butter; 1 bag (30 oz) frozen country-style shredded hash brown potatoes, thawed; 1 can (10 3/4 oz) condensed cream of chicken soup; 1 container (16 oz) sour cream; 2 cups shredded Colby- Monterey Jack cheese blend (8 oz); 1 package (8 oz) diced cooked ham; 1 jar (4 oz) diced pimientos, drained; 2 tablespoons coarse-grained Dijon mustard; 1/2 teaspoon salt; 1/2 teaspoon pepper; Chopped fresh chives, if desired