Preheat oven to 400ºF. While the oven is coming up to temperature, pierce both squash all over with the tines of a fork and microwave each for 3 minutes. Carefully cut each squash lengthwise and scoop out and discard the seeds.

Drizzle or brush each squash half with olive oil and season with salt and pepper on the exposed sides. Place them cut side down (skin side up) on a foil-lined baking dish or rimmed pan. Roast for 45 minutes or until the flesh is tender and the squash starts to caramelize along the edges.

Remove from oven and set aside to cool.

Meanwhile, chop the veggies and mince the garlic and sage. Heat butter in a soup pot or Dutch oven over medium heat. Add all of the chopped veggies and stir to coat with butter. Cook until soft and fragrant, 5 to 7 minutes. Add the minced garlic, stirring to combine and allowing to cook another minute or two. Sprinkle in the fresh sage, salt and pepper; stir once more to incorporate everything.

When the squash is cool enough to handle, scoop out the flesh with a spoon and add it to the pot with the veggies. Stir to combine. Add vegetable broth and turn up the heat to bring everything to a boil. Once it starts to bubble, turn the heat back down and simmer 10 minutes (or more, depending on how much you’d like to develop the flavor). Turn heat off and add milk.

Process with an immersion blender directly in the pot or carefully transfer the soup to a traditional blender and puree in batches. Once a desired consistency is reached, heat the soup on medium low until everything is warmed through and serve.