In a bowl, combine the cheeses and mix until blended. Set aside.
On a large work surface, lay out the bread slices and spread them
evenly with the butter. Then turn them buttered-side down on the
surface and spread the other side thinly with the mustard.
Sprinkle half of the cheese mixture evenly onto the mustard-spread
side of 4 of the slices. Lay 2 tomato slices atop each cheese-topped
slice and then sprinkle the remaining cheese evenly over the tomatoes.
Top the sandwiches with the remaining 4 slices of bread, mustard
side down, and press down gently to compact the sandwiches.
Heat a large nonstick frying pan or griddle to medium heat. Working
in batches if necessary and using a spatula, carefully transfer
the sandwiches to the hot pan or griddle. Cook, pressing down gently
on each sandwich with the spatula 3 or 4 times, until golden and
slightly crusty on the first side, 3-4 minutes. Carefully turn over
the sandwiches and continue cooking, again pressing down on them,
until the second side is golden and the cheese has begun to ooze
out the sides slightly, 2-3 minutes longer.
Transfer to individual plates and serve immediately.
Recipe reprinted by permission of Weldon Owen. All rights reserved.