Best Colcannon

Name: Best Colcannon
Prep time: 15 min
Total time: 15 min
Cuisine: American
Ingredients: 5 medium Yukon Gold potatoes, peeled and cut into 2" pieces; Kosher salt; 6 tbsp. butter, divided; 4 scallions, white parts thinly sliced, greens sliced into 1-inch pieces; 3 cloves garlic, crushed and chopped; 1 large bunch kale, stemmed and sliced into 1/2" ribbons; 3/4 c. milk; 1/2 c. heavy cream; Freshly ground black pepper