Peel the potatoes or leave the skin on, depending on your preference, and dice them into small, uniform pieces. Cook them in a medium pot with salted simmering water until tender but still firm (10-12 minutes).
Hard boil eggs in a saucepan with simmering water for 8-10 minutes, or until the yolks are set. Then, transfer them to an ice bath to stop the cooking process. Once cooled, peel and dice the eggs.
As far as the potatoes, drain and lay them over a rack to cool down completely.
Dressing
Mash 1 cup of cooled potatoes in a large bowl. Add dressing ingredients and mix well. Then, add red onion, celery, cilantro, remaining potatoes, and eggs; mix until combined. Season with salt to taste.
Chill in the fridge for 1 hour, then garnish with cilantro, red onion, and Cotija cheese before serving.