Add 2 tablespoons of oil to a skillet and preheat at medium for a few minutes. Add the potatoes. Spread them out evenly and season lightly with salt and pepper. Cover the skillet and cook for 15 minutes, stirring now and then. Remove from heat and reserve.
At the same time, preheat a large pot at medium heat for a few minutes. Add 1 pound of ground chuck or sirloin. If needed add a drizzle of oil. Season with 1 tsp. salt, 1 tsp. pepper, 1 tsp garlic powder and ½ tsp. cumin. Using a wooden, flat edge spoon, break up the beef and mix with spices. Cook for 7-10 minutes.
To the beef, add the onion and garlic. Stir to combine and saute for 4 minutes. Mix in the carrots, poblano and squash. Add a pinch of salt. Saute for 3-4 minutes.
While vegetables are cooking, transfer the chopped tomatoes, serrano, oregano, 2 cups water and 2 tsps. of bouillon to the blender. Blend until smooth. If you don't want to use bouillon, season with salt, to taste.
Pour the blended tomatoes into the pot with beef and vegetables. Stir well to combine. When it comes up to a boil, taste for salt. Adjust if needed. Add the reserved potatoes back in. If you like your picadillo more soupy, you could add a little more broth or water combined with beef(or chicken) bouillon. Cook at a steady simmer for 15 minutes.
Serve picadillo with a side of rice, beans and warm tortillas.