Step 1

In a large saucepan, melt the butter over low-medium heat until foamy. Stir constantly and cook until it’s brown and smells nutty, about 5-7 minutes. Remove the pot from the heat and let it cool for 2-3 minutes.

Step 2

In a large mixing bowl, combine the brown and white sugars. Add the browned butter and whisk it by hand until blended and smooth. Place the bowl in the fridge for 10-15 minutes.

Step 3

When the brown butter and sugars have cooled, add the egg, egg yolks, and vanilla and whisk well until fully combined.

Step 4

In a separate bowl, stir the flour, oats, baking soda, salt, and cinnamon to distribute the ingredients evenly.

Step 5

Add half of the dry mixture to the wet ingredients and stir with a spatula until it's mostly combined. Then, add the rest of the dry ingredients, chocolate chips, and chopped nuts (if using), and stir until it's just combined.

Step 6

Portion the cookie dough into 2 tablespoon balls. Arrange them on one parchment-lined baking sheet (without spacing), cover with plastic, and chill for 30 minutes.

Step 7

Preheat the oven to 325 degrees Fahrenheit (160°C) and line a second baking sheet with parchment paper.

Step 8

Divide the firm cookie dough balls between the 2 sheets, leaving at least 2 inches between each one. For thicker cookies, leave them as is. For thinner cookies, flatten them slightly with the bottom of a glass. Bake for 10-12 minutes until golden around the edges.

Step 9

Let the cookies cool on the baking trays until they're firm enough to move. Then, transfer them to a wire rack to cool completely. Serve and enjoy!