Step 1

Preheat the oven to 400 degrees F.

Step 2

Oil the squash halves with 2 tablespoons oil and sprinkle with salt and pepper, then place them cut side up on a rimmed baking dish. Cook until the squash is fork-tender, about 30 minutes.

Step 3

Meanwhile, heat the remaining tablespoon oil in a large skillet over medium-high heat, then add the sausage and cook, crumbling it as it cooks, 8 to 10 minutes. Remove to a bowl. Add the mushrooms, onions, garlic and sage to the skillet. Cook, stirring, until the mushrooms have released their moisture and the onions have softened, 5 minutes. Add the chard and season with a pinch of salt and pepper, then stir well. Transfer to the bowl with the sausage. Add the grains, cheese and parsley, then stir to combine.

Step 4

Remove the squash from the oven, then divide the filling mixture among the squash halves. Return them to the oven and bake for an additional 10 minutes.

Step 5

Serve garnished with parsley.