Place the potatoes in a pot and cover with cold water and 1 Tbs salt. Bring to a boil and cook for 20-25 minutes or until tender. Drain.
Heat butter and oil in a large skillet over medium heat. Add the onion and jalapeno and saute for about 5 minutes. Add garlic and cook for another 30 seconds. Stir in chile powder.
Add potatoes to the skillet. Season with salt and black pepper. Stir to combine while gently smashing some of the potatoes. Press into an even layer and cook for about 5 minutes or until golden brown on the bottom. Flip and cook for another 5 minutes on the other side.