How to Make It
Preheat oven to 425°.
Place potatoes in a large saucepan; cover with cool water to 2 inches above potatoes. Bring to a boil. Reduce heat, and simmer 20 minutes or until almost tender; drain. Place potatoes on a work surface, and crush each with a thick, sturdy glass; you want the potatoes broken open but still fairly intact. Sprinkle with vinegar and 1/8 teaspoon salt.
Heat a large heavy skillet over medium heat. Add bacon; cook 3 minutes or until almost crisp. Add shallots to pan; cook 2 to 3 minutes or until bacon is crisp and shallots are browned, stirring occasionally. Remove bacon and shallots from pan with a slotted spoon, reserving any drippings. Add 2 teaspoons oil to drippings in pan. Increase heat to medium-high. Add potatoes in an even layer; cook 2 minutes or until potatoes begin to lightly brown on bottom. Add kale, 1/4 cup stock, and rosemary. Reduce heat to medium. Cover and cook 2 minutes or until kale is almost tender (you want it still chewy). Uncover and drizzle with remaining 1/4 cup stock if too dry; it should be a bit moist. Stir in reserved bacon mixture, 1/4 teaspoon salt, and 1/4 teaspoon pepper. Keep warm.
Sprinkle tops of salmon fillets with remaining 3/8 teaspoon salt and remaining 1/4 teaspoon pepper. Heat a large cast-iron skillet over medium-high heat until a drop of water evaporates quickly when dropped on it. Add remaining 1 teaspoon oil to pan; swirl to coat. Add salmon fillets, skin side down; cook, without turning, for 3 minutes. Place pan in oven (salmon should still be skin side down); cook 7 minutes or until a thermometer registers 130° and salmon is still medium-rare within.
Just before serving, add half-and-half to potato mixture; stir gently just to incorporate. Immediately place 1 cup potato mixture on each of 4 plates; top each serving with 1 salmon fillet, skin side up. Garnish each serving with a parsley sprig.