In a medium saucepan over medium heat, melt the butter, stirring constantly until it turns golden brown and gives off a nutty aroma. Remove from heat and let it cool slightly. This step is critical—the browned butter is what elevates these cookies from ordinary to extraordinary, giving them a deep, caramel-like flavor.

In a large mixing bowl, whisk together the brown sugar, granulated sugar, and cooled brown butter until combined. Add the eggs one at a time, whisking after each addition, then stir in the vanilla extract. The mixture should be smooth, thick, and aromatic.

In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry mixture to the wet ingredients, mixing until just combined. Avoid overmixing to maintain soft, tender cookies.

Gently fold in the chopped Cadbury chocolate eggs and optional nuts. Be careful not to overmix to preserve the integrity of the chocolate pieces, allowing them to melt into perfect pockets during baking.

Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat. Using a cookie scoop or spoon, drop dough balls about 2 tablespoons each onto the baking sheet, leaving enough space for spreading. Even spacing ensures uniform baking and keeps cookies from merging together.

Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden but the centers remain soft. Remove from the oven and let the cookies cool on the sheet for 5 minutes before transferring to a cooling rack. The slight underbaking keeps them chewy and soft.

Enjoy warm for gooey chocolate goodness, or store in an airtight container for up to 3 days. These cookies pair perfectly with a glass of milk, hot cocoa, or coffee for a cozy treat.