Line a cooking sheet with parchment paper. Place small spoonfuls of peanut butter onto the parchment, using the back of the spoon to spread into small discs. Place in freezer for 10 minutes to set. Top discs of peanut butter with Nutella, spreading to meet the edges of the peanut butter. Return cookie sheet to freezer for at least 30 minutes, allowing discs to harden.
Whisk eggs with melted butter. Add yogurt and milk and continue whisking until smooth. Add dry pancake mix and whisk until all lumps are gone.
Preheat griddle to 325 degrees (or place skillet over medium heat) and pray with nonstick cooking spray. Scoop 1-2 tablespoons of batter onto the hot surface, spreading slightly. Cook the first side until it starts to bubble, about a minute, then place one of the frozen peanut butter-Nutella discs into the center of the pancake. Top with another small spoonful of batter to cover the surface; cook for another 1-2 minutes.
Use spatula to flip and cook the second side for an additional 2 minutes. Repeat until all pancakes are made. Serve warm to maximize the ooey-gooeyness!