Heat a large iron or nonstick skillet with an oven-safe handle to medium. Add about a tablespoon of olive oil.

Sauté the sliced mushrooms until they start to brown and give off some of their moisture.

Add the shallots and continue to sauté until the shallots have started to soften and cook. You don't want to cook the shallots as long as the mushrooms, as shallots become bitter if they brown too much.

When the shallots have softened, add the ham and cook until it has started to slightly brown.

Then add the fresh thyme. Sauté for a minute to bloom the herbs.

Remove the mushroom, shallot, and ham mixture. Place in a small bowl and set aside.

Turn your oven on to broil.

Add 2 tablespoons more olive oil to the skillet. Then add the sliced polenta. It is ok to crowd them to fit them all in. Cook the rounds for 2-3 minutes until they start to crisp on one side.

Flip each of the rounds and continue to cook until the other side of each round has crisp golden edges.

Take off heat and spoon some of the mushroom mixture over each polenta round. Distribute all of the mixture evenly.

Add a few drops of lemon juice to each of the mounds of mushrooms.

Sprinkle each of the rounds with some of the gruyere cheese.

Place under the broiler for just a few seconds to melt the cheese and warm the mushroom mixture slightly.

Serve immediately while hot.

If you don't have a skillet with an oven-safe handle, you can omit the broiler part and let the rounds continue to cook for a minute more on the stove with the mushroom mixture added. The cheese will not melt as much but will still be delicious.