Chop the mushrooms into ½” pieces. Heat the olive oil in a large skillet over medium-high.
Add the mushrooms and garlic and cook, stirring a little, but letting the mushrooms brown on the bottom of the pan. Cook this way for about 5 minutes.
Add the thyme, salt, pepper and turn the heat down to medium-low. Add the butter, sherry, vinegar and parsley and continue to cook another 5-10 minutes until the mushrooms are soft-cooked through. Taste for salt.
At this point you can turn the heat off and set the pan aside until you are ready to eat. This can be done a day ahead and reheated.
Assemble the toasts:
Have the cheese at room temperature.
Slice the bread across in ¼” thick slices. Cut the slices in half so that you have toasts in about 3” rectangles.
Toast the bread on a baking sheet in the oven until just crispy, OR (Jane’s lazy way) pop them in a toaster.
Once you have this done, warm the mushrooms in the pan back up so they are nice and hot.
Spread about 1 Tbl. of cheese on the toast. Top with mushrooms.
Serve on a platter and enjoy!