- In a medium skillet, melt 1 tablespoon butter on medium-high.
- Add mushrooms and cook for 3 to 4 minutes; add onion and cook for an additional 3 to 4 minutes; then add kale and red pepper flakes; sauté until onion is translucent and kale has softened.
- Season with kosher salt to taste and remove from heat.
- Wipe skillet and heat on medium-high.
- Butter one side of each slice of bread.
- Place 1 bread slice butter-side down onto skillet bottom and add 1 slice of cheese, then mushroom-kale mixture, then 1 more slice of cheese.
- Place second slice of bread butter side up on top of sandwich.
- Grill until bottom bread is lightly browned and flip over; continue grilling until cheese is melted.
- Repeat to make a second sandwich.
Approximate Nutrient Analysis per serving (based on Swiss Cheese):
650 calories, 42 g fat, 21 g saturated fat, 170 mg cholesterol, 650 mg sodium, 46 g carbohydrate, 1 g fiber, 2 g sugar, 21 g protein