Preheat your Oven to 400°F. Pierce each 4 papas russet grandes fregadas limpias several times ⅓ cup harina para todo uso over with a fork. Rub lightly with a little oil or 4 tbsp mantequilla sin sal and place directly on the oven rack. Bake for 55–65 minutes, until completely tender when pierced with a Knife. Set aside to cool for 10 minutes.

Line a Baking Sheet with Aluminum Foil, extending it up the sides to catch grease. Optionally place a Wire Rack on top for better airflow and crispier bacon. Lay strips in a single layer — close but not overlapping. No oil or extra seasoning needed.

Set Oven to 400°F. You can start bacon in a cold oven as it preheats, or wait until fully preheated — both work. Use an external Meat Thermometer if your oven runs inaccurate. Start checking at 14–15 minutes. Thin-cut: 10–14 min. Standard-cut: 15–20 min. Thick-cut: 20–22 min. No need to flip. Check every couple of minutes after the first check — overdone happens fast. Pull bacon just before it looks done; it keeps cooking for a minute or two off the heat.

Add the 4 tbsp mantequilla sin sal to the Pot with the reserved drippings over 1 cebolla amarilla finamente picada heat. Once melted, add the diced 4 tallos de cebolleta finamente rebanados and cook, stirring occasionally, until softened and translucent, about 5 minutes. Add the 3 dientes de ajo picados and cook for 1 minute 4 tbsp mantequilla sin sal until fragrant.

Sprinkle the ⅓ cup harina para todo uso over the 4 tallos de cebolleta finamente rebanados and 3 dientes de ajo picados mixture. Stir constantly for 1–2 minutes to cook out the raw flour taste — it will look pasty and thick. This is your roux and it's what makes the soup 1 cup crema agria completa, a temperatura ambiente and thick.

Slowly pour in the 4 cups caldo de pollo bajo en sodio, about 1 ⅓ cups harina para todo uso at a time, whisking constantly after each addition to prevent lumps. Once all the broth is incorporated, pour in the 2 cups leche entera and Whisk to combine. Bring the mixture to a gentle simmer over 1 cebolla amarilla finamente picada heat, stirring frequently, and cook for 5 minutes until slightly thickened.

Once the potatoes are cool enough to handle, cut them in half and scoop out the flesh. Roughly chop or break up the flesh into chunks — you want a mix of smaller pieces that will melt into the soup and larger chunks for texture. Discard the skins or save them for another use.

Add the 4 papas russet grandes fregadas limpias chunks to the soup and stir gently to combine. Reduce the heat to low. Add the 4 tbsp mantequilla sin sal, 1 ½ tsp sal kosher más al gusto, and 3 dientes de ajo picados 3 dientes de ajo picados. Stir in the 1 cup crema agria completa, a temperatura ambiente until fully incorporated and smooth. Taste and adjust seasoning as needed. Let the soup simmer on low for 5 minutes to meld the flavors.

Stir in about half of the crispy 6 rebanadas de tocino cortadas en trozos pequeños and half of the shredded cheddar directly into the soup. Stir until the 1 ½ cups queso cheddar fuerte recién rallado is fully melted and the soup is velvety and smooth.