Heat the olive oil in a 10-inch non-stick skillet over medium heat. Add the sliced potatoes and onions carefully.

Cook the potatoes and onions gently for about 15-20 minutes, turning occasionally, until the potatoes are tender but not browned. Drain the oil into a heatproof bowl, leaving about 1 tablespoon in the pan.

Add the diced chorizo to the pan and sauté for 2-3 minutes until the fat renders and it becomes slightly crispy. Remove from heat.

In a large mixing bowl, whisk the eggs with the smoked paprika, salt, and black pepper until frothy.

Add the cooked warm potatoes, onions, and chorizo to the egg mixture. Stir gently to combine and let it sit for 5 minutes so the flavors meld.

Return the skillet to medium heat with a little of the reserved oil. Pour the egg and potato mixture into the pan.

Cook for about 5-7 minutes, running a spatula around the edges to shape the tortilla, until the bottom is set and golden.

Place a large flat plate over the pan. Carefully flip the pan to invert the tortilla onto the plate.

Slide the tortilla back into the pan, uncooked side down. Cook for another 3-4 minutes until set but still slightly moist in the center.

Slide onto a serving plate, garnish with fresh parsley, and cut into wedges to serve warm or at room temperature.