Boil the potatoes: Place the baby Yukon Golds in a large pot, cover with cold salted water by 2 inches, and bring to a boil. Cook for 15-18 minutes until a knife slides through with zero resistance. Drain and let them steam dry for 2 minutes.
Smash the potatoes: On a cutting board, press each potato flat with the bottom of a heavy mug or measuring cup until about 1/2 inch thick. They should crack and split around the edges — that is where the crunch comes from. Season both sides with salt, pepper, smoked paprika, and cumin.
Crisp the potatoes: Heat 2 tbsp olive oil in a large 12-inch cast iron skillet over medium-high heat until shimmering. Add the smashed potatoes in a single layer — do not crowd. Cook without moving for 4-5 minutes until the bottoms are deeply golden and crispy. Flip and crisp the other side for another 3-4 minutes. Remove to a plate.
Cook the chorizo: In the same skillet, add the remaining 1 tbsp olive oil. Crumble in the fresh chorizo and cook over medium-high heat for 5-6 minutes, breaking it into small pieces with a wooden spoon, until browned and the fat has rendered. The chorizo oil is flavor — do not drain it.
Add the vegetables: Toss in the diced bell pepper and onion. Cook for 3-4 minutes until softened and starting to char at the edges. Add the minced garlic and cook for 30 seconds until fragrant.
Combine: Return the crispy smashed potatoes to the skillet and toss gently with the chorizo and vegetables. Press everything into an even layer and let it sit undisturbed for 2 minutes to build one more layer of crust on the bottom. The hash should be sizzling and smell incredible.
Fry the eggs: Push the hash to the edges to create 4 small wells, or use a separate nonstick pan if you prefer. Add butter, crack the eggs into the wells, season with salt and pepper, and cook for 2-3 minutes until the whites are set and the edges are lacy but the yolks are still runny.
Serve straight from the skillet: Top with crumbled cotija, chopped cilantro, sliced scallions, sliced avocado if using, a squeeze of lime, and a generous shake of hot sauce. Bring the whole skillet to the table and let people dig in — this is not a plated-nicely kind of breakfast.