Sweat the chopped onion in the lard until translucent, take off the heat, and stir in the paprika.
Return to the heat, add the large-cubed potatoes, salt, and fry a few minutes so the paprika-fat coats them.
Pour in a little water, cover, and steam over low heat until the potatoes are half-tender, about 15-20 minutes, stirring occasionally.
Once half-tender, pour over the sour cream and finish steaming until the potatoes are fully tender, another 8-10 minutes, but don't let it boil hard so the sour cream doesn't curdle.
Serve hot.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.