Cookie Cups:

• Preheat the oven to 350°F (177°C). Lightly coat a nonstick mini muffin tin with cooking spray and set aside.
  cooking spray
• In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter, brown sugar, and granulated sugar together until creamy and fully combined. Add the egg yolks and vanilla extract and continue mixing until smooth and evenly blended.
  ½ cup (113 g) unsalted butter, ½ cup (110 g) firmly packed light brown sugar, ¼ cup (50 g) granulated sugar, 2 large eggs yolks , 1 tsp (5 ml) vanilla extract
• In a separate bowl, whisk together the flour, baking soda, and salt. Add the dry ingredients to the butter mixture along with the mini chocolate chips and mix just until combined, scraping down the sides of the bowl as needed.
  1 cup (125 g) all-purpose flour, ½ tsp (2.5 g) baking soda, ½ tsp (3 g) table salt, 1 cup (170 g) mini semi-sweet chocolate chips
• Scoop about 1 tablespoon (20 g) of dough into each prepared muffin cup. Use your thumb or the back of a spoon to press a shallow indentation into the center of each portion, gently pushing the dough up the sides to form a cup shape. Bake for 10 minutes.
• Remove the muffin tin from the oven and immediately press the centers of the cookie cups down again to reinforce the wells. Return the pan to the oven and bake for an additional 3 minutes. Remove from the oven and, if needed, gently press down any areas of the centers that have risen. Allow the cookie cups to cool completely in the pan so they set and hold their shape.
• While the cookie cups cool, place the dark chocolate chips and Nutella in a heat-safe bowl and set aside. In a small saucepan over medium heat, warm the heavy cream until small bubbles begin to form around the edges, being careful not to let it boil. Immediately pour the hot cream over the chocolate and Nutella and let it sit undisturbed for 10 minutes.
  ½ cup (85 g) dark chocolate chips, 1 cup (300g) Nutella, 1 cup (240 ml) heavy whipping cream
• After resting, whisk the mixture until smooth and fully blended. The filling may look uneven at first, but it will come together as the chocolate melts and incorporates. Once the mixture thickens slightly but remains spoonable, fill each cooled cookie cup with the chocolate filling.
• Allow the filled cookie cups to set at room temperature or refrigerate briefly until the centers are softly set. When ready to serve, top with whipped cream, mini chocolate chips, or chopped hazelnuts if desired.
  whipped cream, mini semi-sweet chocolate chips, chopped hazelnuts