Mix kimchi, ketchup and mayonnaise in small bowl to make a sauce; set aside. Halve Italian sausage link lengthwise and then halve crosswise to yield 4 sausage pieces, each with a flat side.
Heat cast iron skillet over medium-low heat. Spread 1 side of each bread slice with some of the butter. Place bread slices in hot skillet buttered-side-down and grill until bottoms are golden brown.
Remove from skillet; spread remaining butter on other side of each slice. Top browned side of 1 bread slice with cheddar cheese curds. Spread kimchi sauce over curds. Top with layer of Italian sausage and Swiss cheese slice. Top with second bread slice, browned-side-down.
With pan still on medium-low, place sandwich in pan, covered. Grill until bottom is golden and cheese begins to melt, about 5 minutes. Carefully flip sandwich; grill until bottom is golden and cheese is melted. Garnish with fennel fronds, if desired.
- 1/2 cup napa cabbage kimchi, chopped
- 1 1/2 tablespoons ketchup
- 1 tablespoon mayonnaise
- 1 sweet (mild) Italian sausage link, cooked whole
- 2 slices multigrain sourdough bread
- 1 1/2 tablespoons butter, softened
- 1/3 cup Wisconsin Cheese Curds
- 1 large slice Wisconsin Swiss cheese
- Chopped fennel fronds, for garnish, optional