Melt 1 tablespoon of the butter in a large skillet over medium-high heat.  Make sure the scallops are dry - you want a good sear on them.  Sprinkle the scallops, each side, with 1/4 teaspoon salt and pepper. 

When the skillet is hot, add the scallops to the pan.  Cook 2-3 minutes per side or until browned. Don't overcrowd them. If you have to, cook in batches.  As they're done, remove from the skillet to a plate. 

Melt the 2 remaining tablespoons of butter to the skillet, still on medium-high heat.  Add the mushrooms and cook for 3-4 minutes or until they're starting to brown.  Add the leeks and garlic.  Cook and stir for another 3-4 minutes or until the leeks are tender. 

Add vermouth, stir, and cook for another 2-3 minutes, until it's almost evaporated. 

Stir in the cream and bring to a boil.  Cook for 1 minute.  Add shredded cheese and remaining 1/4 teaspoon salt and pepper.   Cook and stir about 30 seconds to melt the cheese.

Return the scallops to the skillet and cook for 1-2 minutes, just until heated through.  Enjoy!