Preheat oven to 425°. Spray a rimmed baking sheet with cooking spray.
Using a sharp knife, cut off ends of potatoes (for a base for canapés). Cut potatoes in half shortways.
In a large bowl, toss together potatoes, 1½ teaspoons olive oil, parsley, ¼ teaspoon salt, pepper, and garlic powder.
Arrange potatoes in a single layer on prepared pan.
Bake until potatoes are tender when pierced with a fork, approximately 15 minutes.
Let cool completely.
Using a sharp knife, butterfly filets.
Rub with remaining 1½ teaspoon salt.
In a medium cast-iron skillet, heat remaining 1½ teaspoons olive oil over medium-high heat.
Add filets and cook until browned, 2 to 5 minutes per side.
Transfer filets to a cutting board, and let rest for 20 minutes.
Using a sharp knife, cut filet into 24 thin slices.
Stand potatoes larger ends up.
Fold a filet slice in half and place on top of each potato.
Top each with a blue cheese wedge.
Garnish with fresh parsley, if desired.