Wipe the mushrooms with a damp paper towel to remove dirt. Thinly slice the mushrooms.
Heat 1 tablespoon butter in a large skillet over medium heat. Add the mushrooms and garlic; saute until lightly browned. Turn the heat up to high, add the wine, and stir until the wine has cooked down and there is hardly any liquid left in the pan. Remove from heat and stir in the parsley.
Heat a griddle or large skillet to medium high heat. Spread the remaining 1 tablespoon butter over the exterior of the 4 slices of bread (melting it first helps it go farther). Place the bread on the griddle, buttered side down, and top with mushrooms and one slice of Provolone. Top with a second slice of bread, buttered side facing up. Grill until golden brown, flip, and repeat. The cheese should be melty and gooey and bread will be crispy on the outside.
For open faced sandwiches, I'd suggest grilling the bread first on the griddle like directed, but then adding the cheese finishing the whole thing in a hot oven for a more even, gooey, picturesque melted cheese topping.
Recipe by Pinch of Yum at http://pinchofyum.com/simple-garlic-butter-mushroom-provolone-melts