Preheat oven to 400°F
Spread half of the melted butter onto a large sheet tray.
Lay 9 slices of the bread onto the sheet pan (overlap the edges.)
BasIl Pesto Panini:
Spread the basil pesto as a base layer, add the tomato slices and the sliced mozzarella balls.
Marinated Grilled Mushrooms Panini:
Place 5 slices of cheddar cheese and the Sliced Marinated Grilled Mushrooms.
Jalapeño Slices Panini:
Sprinkle ½ cup of cheddar cheese and the Sliced Jalapeños.
Lay another 9 slices of the bread on top, to close the sandwiches (overlap the edges.)
Spread the remaining melted butter over top of the bread.
Place a second sheet pan over all the sandwiches. Use a heavy oven safe object (like a cast iron pan), to squish the sandwiches.
Bake for 25 minutes. Remove the heavy objects and the top sheet pan, and bake for another 10 minutes or until the bread is golden brown.
Remove the sandwiches from the oven, slice into squares, serve and enjoy!