Season the chicken with salt and pepper, and set aside for about 10 minutes
In a 5.5 quart Dutch oven, or heavy bottom pan, heat the olive oil on medium to high heat.
Add half of the chicken legs to brown on both sides, when they're light golden brown, remove them from the pan, and set aside on a plate. Repeat this process with the other half of the chicken legs.
Drizzle some more olive oil in the pan, then reduce the heat to medium. Add in the diced onions, the white part of the scallions, and saute until soft.
Next add in the Brazilian sofrito or the garlic, and saute until fragrant.
Add in the paprika and the ground mustard powder, then stir to combine. Let it cook for about a minute, then add in the vinegar to deglaze the pan.
Let the vinegar reduce in half, then add the chicken back to the pan. Stir to coat and cook until the acid evaporates.
Sprinkle in the flour, and stir to combine.
Add in the potatoes, the chicken stock, the bay leaf and the thyme - give everything a stir and make sure everything is submerged in liquid.
Bring everything to a quick boil, then reduce to low heat, cover and simmer until the potatoes are cooked - about 20 minutes.
Uncover the pan and add in half of the green onions. Stir and continue to simmer until the liquid thickens, another 40 minutes to an hour.
Add in the rest of the green onions and the butter. Stir to combine. Turn off the heat, taste and adjust salt and pepper if needed.
Serve with rice or crusty bread!