Preparation Place 4 bread slices on work surface. Spread 1 tablespoon miso over each. Top each with 2 tomato slices, then 1 onion slice and 3 basil leaves. Sprinkle each with 1/3 cup cheese. Top with remaining bread slices, pressing lightly to adhere. Spread 1/2 teaspoon butter over top of each sandwich. Heat 2 large nonstick skillets over medium-low heat. Add 2 sandwiches, butter side down, to each skillet. Cover and cook until bread is golden brown on bottom, about 4 minutes. Spread top of each sandwich with 1/2 teaspoon butter. Turn sandwiches over; cover and cook until bottoms are brown and cheese melts, about 3 minutes. Cut sandwiches crosswise in half and serve.
Preparation Place 4 bread slices on work surface. Spread 1 tablespoon miso over each. Top each with 2 tomato slices, then 1 onion slice and 3 basil leaves. Sprinkle each with 1/3 cup cheese. Top with remaining bread slices, pressing lightly to adhere. Spread 1/2 teaspoon butter over top of each sandwich. Heat 2 large nonstick skillets over medium-low heat. Add 2 sandwiches, butter side down, to each skillet. Cover and cook until bread is golden brown on bottom, about 4 minutes. Spread top of each sandwich with 1/2 teaspoon butter. Turn sandwiches over; cover and cook until bottoms are brown and cheese melts, about 3 minutes. Cut sandwiches crosswise in half and serve.