If using a whole butternut squash, carefully peel it and cube the flesh into one-inch pieces. Peel and slice the onion into wedges. Peel the garlic cloves and smash them by placing each clove (one at a time) on a cutting board, resting your chef's knife on top of it (sharp side pointed away from you), and then smacking the palm of your hand on top of the flat edge (not the sharp edge, but please do be careful regardless) of the knife.
Place the cubed squash, onion, and garlic on the sheet pan. Add the olive oil, thyme, and a pinch of salt and pepper. Toss to evenly coat.
Roast for 30-35 minutes - you want the squash to be tender, but the soup will be a lot more flavorful with some color (caramelization) on the squash, onions, and garlic.
Remove from oven and let cool about 5-10 minutes, or until cool enough to more easily handle.
Transfer all of the roasted vegetables on the sheet pan to a blender and add the broth. Blend on medium-high speed for 1-2 minutes, until soup is pureed quite smooth.
Serve and enjoy!
Please refer to the blog post for notes on leftovers, freezing, reheating instructions, make ahead and meal prep tips.One serving is 6 ounces (¾ cup).