The key to Mukimo is that all ingredients – potatoes, corn, and greens – are cooked together and then mashed together, resulting in a coarse yet homogeneous mixture with visible corn kernels.
Traditionally, tender leaves (such as pumpkin or nettle leaves) are used, but for accessibility, baby spinach or collard greens are ideal substitutes.
In a large pot, place the potatoes, corn, and salt. Cover with cold water until the vegetables are just submerged.
Bring to a boil and cook for 15 minutes. Add the chopped onion and green leaves (spinach/collard greens). Cook for another 10–15 minutes until the potatoes are completely tender.
Drain most of the water from the pot, but save about 1/2 cup in case the mash is too dry. Only the vegetables should remain in the pot.
Add butter or oil.
Using a potato masher, vigorously mash the mixture. The goal is to mash the potatoes and leaves, but not completely break the corn kernels. Mukimo should be coarse and slightly elastic.
If the mash is too dry or stiff, gradually add the reserved hot water. If it is too runny, cook it for a little longer over low heat until the excess water evaporates.
Taste and add more salt if necessary.
Serve warm as a side dish.