Chipotle Cheddar Grilled Cheese with Andouille Sausage & Smashed Avocado

andouille sausage link, (chicken or pork) sliced 4 slices sandwich bread (sourdough or other crusty bread) Butter, for toasting 1 avocado, smashed with a pinch of kosher salt 4 ounces chipotle cheddar cheese, coarsely shredded (I use Cabot)