In a small bowl, mix together the mayonnaise, mustard, garlic, and rosemary. Add a little salt to taste. Set aside for up to 30 minutes at room temperature or up to 1 day refrigerated.

To assemble
Place the bottom half of each croissant on your work surface, cut side up. Spread 2 tablespoons of the mayonnaise mixture on each croissant half followed by the sun-dried tomatoes. Lay the Brie slices on top, followed by the Swiss Cheese and turkey slices. Top with the remaining croissant halves, cut side down.

For stovetop method
Heat a large nonstick skillet over a medium-low heat for 2 minutes. Put the sandwiches into the pan, cover, and cook for 2 to 3 minutes, until golden brown. Carefully turn the sandwiches, pressing each one with a spatula to compress the bread and filling. Cover and cook for 2 to 3 minutes or until the undersides are golden brown. Turn the sandwiches once more, press with the spatula again, cook for 1 minute, and remove from the pan. Let cool 5 minutes. Cut in half and serve.

For sandwich maker method
Preheat the sandwich maker. Follow directions for assembly above. Cook according to manufacturer’s instructions.
Note: The weight of the lid of some sandwich makers might be too heavy for the delicate croissant. You may want to experiment with one sandwich before cooking the rest.

Note: If you can only find regular-size croissants, you may end up with filling for more than 4 sandwiches. Also, be aware that because of their high butter content, croissants can burn easily. Watch carefully.