Chicken Sliders with Pasilla Peppers and Chipotle Ketchup

Ingredients (13)

• 1 pound ground chicken thighs
• 2 tablespoons fresh oregano leaves
• 1 teaspoon kosher salt
• 1 teaspoon freshly ground pepper
• 4 slices Havarti cheese
• 1 pasilla pepper
• 1 onion
• ½ tablespoon butter
• ½ tablespoon canola or vegetable oil
• 8 slider buns
• ½ cup ketchup
• 1-2 canned chipotle peppers plus adobo sauce
• 1 cup arugula