Step 1: Preheat your oven to 350°F (175°C).
Step 2: Line two baking sheets with parchment paper.
Step 3: In a large mixing bowl, combine Nutella, peanut butter, and sugar. Beat until smooth and creamy.
Step 4: Add the eggs one at a time, mixing well after each addition.
Step 5: Gradually add flour to the wet mixture and mix until just combined.
Step 6: Scoop the dough onto the baking sheets, spacing them about 2 inches apart.
Step 7: Bake for 10-12 minutes, until edges are golden but centers are soft.
Step 8: Cool cookies on the baking sheets for 5 minutes, then transfer to a cooling rack.
Step 9: Once cool, spread frosting on the bottom of one cookie and top with another to make a sandwich.