Also surprisingly, I couldn't find these fresh, either. Of course, they thaw out very quickly, so that worked out just fine.
After marinating all day, pull the scallops out, and if you have bay scallops, go on and pat them dry. If you have larger scallops, like these, just quarter them up to be roughly the size of a bay scallop.
Pat your scallops dry, and while you're doing that, in a heavy bottomed pan, melt 2 Tbs. of butter. Also, while you're starting this, get your water on to boil for your pasta. Once your pasta water comes up to boil, salt it with about 1 Tbs of salt, and boil your pasta to one minute shy of the package directions (ie if the box says to boil for 9 minutes, boil for 8 minutes).
Once your butter has melted, put your scallops in, in an even layer, and let these cook for about 3-4 minutes, then turn them over (as best you can. These are pretty small, so just scoot them around the pan, and they will brown on all sides this way), and cook for another minute or so. Scallops cook pretty quickly.
Scoop your scallops out, and set them on a paper towel lined plate; add in the mushrooms and cook these for 4-5 minutes until beautifully browned. Scoop these out as well, and put them on the paper towel lined plate, with the scallops.
Now then, let's get started with building the sauce. Melt the other 2 Tbs. of butter, and add in the 2 Tbs. flour, and mix together until it is a peanut butter color.
Once this roux has thickened up, pour in the white wine. It will look a little lumpy, but that's fine, it will mix together into a smooth sauce.
Add in the milk, about 1/2 C at a time, stirring or whisking the whole time. Again, it may look pretty lumpy, but that's okay, trust me.
Once all of your milk has been added in, pour in the heavy cream, and mix that in as well. Now that you have a beautiful, creamy sauce, start adding in your cheeses, slowly. Like I explained in my cheesy chicken quesadillas post, you have to add the cheese in slowly, or else you'd end up with a clump of cheese, surrounded by sauce. If you add the cheese in a little bit at a time, it melts into the sauce and because a beautiful cheese sauce.
The more cheese you add, the more cheese you can add to your sauce in each addition. Once all of my fontina cheese has been added, I added the shredded cheddar cheese in pretty quickly. I saw the finish line in my future, and wanted to slam my face into this as soon as possible.
Since spinach wilts down a lot, and very quickly, I just added it in when I stirred my cooked pasta, and it was prefect. So, now that all of your cheeses have been added to your sauce, add in the pasta, spinach, scallops, and mushrooms and mix well.