Other optional additions: Pickled Onions, anchovy fillets, capers
Instructions
If you'd like to eat the sandwich warm, place a rack in the center of the oven and preheat to 400°F. Line a baking sheet with parchment paper.
Split the baguette in half horizontally. With your fingers, remove some of the inner bread from the top and the bottom so you have more room for the filling. Place cut sides up on the baking sheet (or a large work surface if not toasting the sandwich in the oven).
In a small bowl, stir together the pesto and the yogurt. Spread all over the bottom of the baguette—it will be a generous layer. If you have a little extra, you can spread it on the top of the bread.
Add the mozzarella slices, tomato slices, and a sprinkle each of salt and pepper. Top with the basil and any other desired toppings. Drizzle on the balsamic and a little olive oil. Add the top slice of bread and press down gently.
Place the sandwich in the oven and let toast for 3 to 5 minutes to warm through. Slice and enjoy immediately.
Notes
TO STORE: Wrap the caprese sandwiches in foil or plastic wrap and refrigerate for up to a day. Note that the bread will likely become soggy due to the moisture from the tomatoes and vinegar.
TO REHEAT: Place the sandwiches back in the oven at 375°F to crisp up the bread and warm the fillings, or simply eat them cold.