Preheat oven to 300 F.
Massage kale leaves with 2 tbsp lemon juice.
Cut squash in half lengthwise and scoop out and discard seeds. Brush interior of squash with olive oil and sprinkle with pepper and sea salt. Place squash halves skin-side up on parchment or foil-lined baking sheet. Bake for 40 - 60 minutes. Let cool for at least 15 minutes.
While the squash is cooling, prepare the stuffing. Combine the quinoa and stock in a saucepan and bring to a boil. Cover, reduce heat to low, and simmer for 15 minutes. Fluff with a fork and set aside.
In a large skillet, season the onion and garlic with salt and pepper and sautee over medium heat until fragrant and soft.
Mix in the kale and cover on medium-low for 3 minutes. When the kale has wilted, add mushrooms with a squirt of lemon juice, pinch of salt, and pepper. Stir well and cover for 10 minutes.
Scoop the flesh from the squash halves, being careful to leave the skin intact.
Mix the squash pieces into the pan and keep covered for another 5 minutes.
Generously fill each squash boat with stuffing and return them to the oven for 5-10 minutes.
Sprinkle with parmesan cheese before serving. Enjoy!