Peel and cut the russet potatoes into 1-inch chunks and place them in a large pot. Cover with cold water and add salt. Bring to a boil, then reduce heat and simmer for 15-20 minutes until fork-tender.

Finely shred the kale and slice the green onions. In a separate saucepan, heat the milk over low heat until it simmers.

Drain the potatoes and return the empty pot to the stove over medium heat to evaporate any remaining water.

Melt the butter in the pot over medium heat, add the shredded kale, and sauté for 3-4 minutes until tender.

Add the sliced green onions to the cooked kale and sauté for another minute.

Pour in the warm milk and add the drained potatoes back into the pot. Mash together until combined, aiming for a rustic texture.

Season with black pepper and more salt if needed. Stir gently to incorporate.

Serve immediately in bowls, optionally garnished with butter.