Heat the olive oil in a large pot over medium heat. Add the shallot and garlic and cook for a few minutes while you prepare the squash.
Wash the acorn squash and slice in half. Remove the seeds (reserve for later if you want to use them as garnish) and cut the squash into rough cubes. You do not need to peel it.
Add the squash to the pot and cook for a few minutes, stirring occasionally, until the squash begins to soften. Add the vegetable stock and short grain brown rice and increase heat to high to bring to a boil. Reduce heat to a simmer, cover the pot, and let it cook for 40-45 minutes, or until the rice is tender and the squash has disintegrated into the risotto. Stir occasionally.
If you reserved the squash seeds, rinse them off in a colander to remove any flesh. Pat dry and toss with 1 teaspoon olive oil and a few dashes of sea salt in a mixing bowl. Spread out on a baking sheet and bake for 15 minutes at 300 degrees F. Set aside to use for garnish.
Take the cover off the pot and stir in the rainbow chard leaves and stems. Cook for 5-10 more minutes (with the pot uncovered), stirring occasionally, until most of the remaining liquid evaporates. Stir in the parmesan and lemon juice. Taste and add salt, pepper, more cheese, or lemon zest as desired.
Transfer to serving dishes, garnish with roasted acorn squash seeds (if you made them), and enjoy warm.