Preheat oven to 400°. Grease a 12-well mini muffin pan with cooking spray.
Line a rimmed baking sheet with paper towels. Place potatoes on pre-pared baking sheet and let thaw. Press all excess moisture out of potatoes.
In a medium bowl, stir together thawed potatoes, Parmesan cheese, green onion, olive oil, ½ teaspoon salt, and pepper. Spoon 1½ tablespoons potato mixture into wells of prepared pan. Press potato mixture into bottom and up sides of wells.
Bake for 20 minutes. Add a Brie piece to each potato cup. Bake until Brie melts and potato cups are crispy and golden brown, approximately 5 minutes more.
Meanwhile, in a medium skillet, cook bacon over medium heat until crisp. Drain on paper towels. Crumble when cool. Reserve ½ teaspoon bacon grease in skillet. Add apple, fennel, red onion, brown sugar, vinegar, and remaining ¼ teaspoon salt. Sauté until soft and fragrant, 3 to 5 minutes.
Gently remove potato cups from pan. Top each potato cup with crumbled bacon and apple mixture.
Garnish with fennel fronds, if desired. Serve immediately.
Recipe by TeaTime Magazine at https://teatimemagazine.com/hash-brown-canapes-recipe/