Make the gravy
In a medium sauté pan, cook mushrooms in 1 tbsp. oil. (They will shrink quite a bit while cooking).
Stir occasionally while cooking over medium-high heat for 5 minutes. Season with salt and pepper.
Add in garlic and butter, stir frequently to keep garlic from burning. Mushrooms will start releasing their liquid, keep cooking until liquid has been reduced to a few tablespoons.
Sprinkle flour over the mushroom mixture and cook for another minute, stirring constantly.
Whisk in the stock, reduce heat and keep whisking until gravy is smooth and thickened.
When gravy has reached desired consistency, remove from heat, cover and set aside.
Make the fries
Using a sharp knife, slice potatoes into planks and then into fries.
Place in a bowl of cold water. Soak the potatoes for a few minutes. The water will get cloudy, drain and rinse again. (This is removing some of the starch from the potato)
Once the potatoes have been rinsed a few times, drain them and pat dry with paper towels.
In a large, deep pot, add enough oil to fill about halfway up. (I use a big stock pot for this)
Heat oil to 300°F, using a thermometer if you have one, to take the temp of the oil. You want the oil to simmer, not a rolling boil.
Once oil has come to the proper temp, GENTLY slide in half of the potatoes.
Using a wooden or metal spoon, move the potatoes around in the oil to ensure even cooking. Cook for 5 - 6 minutes, then remove from oil using a spider (skimmer) and drain on fresh paper towels. Repeat with remaining potatoes.
Increase oil temperature to 400°F/200°C. Carefully lower fries back into the hot oil for the final cooking. Oil should be at a full boil. Carefully move them around in the pot so they brown evenly.
Once they are deep golden brown, remove and place on paper towels to drain. Sprinkle with salt immediately.
Top fries with cheese curds, then cover with mushroom gravy. Garnish with parsley, if desired. Serve immediately.