Vegetarian Reuben

Name: Vegetarian Reuben
Cuisine: American
Ingredients: 2 Tbsp. extra-virgin olive oil; 4 garlic cloves; 2 bunches Tuscan kale, center ribs and stems removed, leaves coarsely torn; 1 cup sauerkraut, drained; ¼ cup whole-milk Greek yogurt; 1 tsp. hot sauce; Kosher salt; 4 slices rye or whole wheat bread; 2 slices Swiss cheese (about 3 oz. total); ¼ cup finely grated Parmesan; 2 Tbsp. unsalted butter, room temperature, divided