¾ cup grated old cheddar cheese (about 150g, divided)
salt and pepper (to taste)
To cook squash:
Roast (cut squash in half, remove seeds and bake cut side down at 400F for about 40 mins) or microwave (pierce skin with sharp knife all over, cook for 10-15 minutes, depending on size, rotating squash halfway through).
Preheat oven to 375F. Heat oil in a large skillet over medium heat. Add onion and sauté until soft, about 4-5 minutes. Add garlic and sauté for additional 1-2 minutes. Add squash, about ¼ tsp salt and ⅛ tsp pepper, sauté for additional 3 minutes. Remove from heat.
In a large bowl, whisk milk, eggs, approximately ½ tsp salt and ⅛ tsp pepper (or to taste). Add squash mixture and ½ cup cheese and stir until well combined.
Transfer mixture into an oiled baking dish (picture is a 1.4L Corningware). Bake for 35-40 minutes until golden brown.