1-Preheat the oven: Preheat the oven to 350°F and position a rack in the center. Line two large baking sheets (15×20 inches) with parchment paper.

2-Melt chocolate and butter: In a saucepan, melt the chocolate chips and butter over medium-low heat, stirring often until smooth. Remove from heat.

3-Beat eggs and sugar: Using a stand or hand mixer, beat the eggs and sugar on medium speed for several minutes until pale, foamy, increased in volume, and thick with a ribbony texture. This step is particularly important at high altitudes as it helps incorporate air for better structure.

4-Add melted chocolate and butter: Add the melted chocolate and butter to the eggs and whisk until combined.

5-Add dry ingredients and vanilla: Add the sifted cocoa powder, vanilla extract, and salt, whisking until combined. The batter will be thin, like brownie batter.

6-Chill the batter: Chill the batter in the refrigerator for 10 minutes to slightly thicken. This brief chilling helps control spreading during baking.

7-Scoop cookie batter: Use a medium cookie scoop (2 tbsp capacity) to place dollops on the baking sheets, leaving 3-4 inches between cookies. The extra space is necessary as these cookies spread significantly at high altitude.

8-Bake the cookies: Bake one pan at a time for about 10-11 minutes until the cookies spread and tops crackle. Watch them closely as baking times can vary slightly depending on your exact elevation.

9-Shape cookies: Immediately after baking, use a round cookie cutter to shape and pull edges inward for perfectly circular cookies. This technique is optional but creates a more uniform appearance.

10-Cool the cookies: Cool on the pan for 10-15 minutes until set, then transfer to a rack to cool completely. The cookies will be thin after cooling, which is characteristic of flourless cookies at high altitude.