Rinse and chop the 4 cups of squash into bite sized pieces. Mince the 1 cup of yellow onion, 1 whole poblano pepper, and 1 cup of brown mushroom into sharp slender pieces by cutting at a diagonal.
In a large frying pan on a medium/high heat, add the squash, yellow onion, poblano pepper, brown mushroom, 1/2 tsp of black pepper, 1/8 tsp of sea salt, and 3 tbsp of olive oil. Cook until contents are tender, about 15 minutes.