Chop carrots into 1 ½-inch pieces and place in a large pot. You do not need to peel them. Add the bone broth, cover with a lid, and bring to a boil over medium-high heat. Lower heat to medium and cook until fork tender, about 15 minutes.

Drain any remaining liquid and transfer carrots to serving dish. Mash to desired chunkiness with a potato masher. Stir in the lemon juice and sea salt.

Sautee the leek and rosemary in the olive oil in the same pot you cooked the carrots in over medium heat until wilted and golden brown at the edges. Top the mashed carrots with the mixture and serve warm.