Preheat 1/8 to 1/4 cup of olive oil in a nonstick pan to medium heat for a few minutes. Add the diced potatoes and cook until browned and crispy in most spots. I like to cover my potatoes while they cook. The steam created helps them cook a little faster from the inside. Transfer potatoes to a plate lined with paper towels to drain, set aside.
Add the ground beef to that same skillet and heat to medium/high. Season beef with 1 teaspoon salt, 1 teaspoon garlic powder, 1 teaspoon cumin and 1/2 teaspoon pepper. Cook for 8 to 10 minutes until nicely browned.
Add the garlic and onion, continue cooking for 2 to 3 minutes. Add tomatoes, serranos, 1/4 cup water, salt and oregano to the blender and blend until smooth. Pour tomato mixture into picadillo. Let it come to a boil and taste for salt. Fold in the potatoes and stir until well combined. Taste for seasonings and continue cooking at a low simmer until sauce thickens and reduces, 7-10 minutes . Remove from heat.