Preheat the oven to 425 degrees F (220 degrees C).
Line two baking sheets with parchment paper.
Toss half the Cauliflower (1 head) florets with Olive Oil (1 tablespoon) and Sea Salt (1/2 teaspoon). Arrange evenly on one baking sheet.
Toss the Cremini Mushroom (1 pound) and Jalapeño Pepper (2) with Olive Oil (1 tablespoon) and Sea Salt (1/2 teaspoon). Arrange in an even layer on the second sheet.
Roast both baking sheets in the oven until the vegetables are caramelized and tender, 25 - 30 minutes, redistributing once halfway through. Set aside.
Meanwhile, in a medium saucepan or pot, bring the Shallot (1) remaining cauliflower, Whole Milk (2 cup), and Sea Salt (1/2 teaspoon) to a simmer. Cook over medium-low heat, covered, until the cauliflower is tender, about 20 minutes.
Puree the cauliflower mixture with an immersion blender, or transfer to a food processor or stand blender, until smooth.
Return to the pot and stir in Monterey Jack Cheese (1 cup). Cook stirring constantly until melted. Add some extra milk or water, if necessary, so the cauliflower queso is a drizzle-able consistency.
Arrange the Tortilla Chips (1 bag) on a baking sheet. Heat in the oven until warm, 2 minutes.
Scatter the veggie mixture on top of the chips and drizzle with the cauliflower queso. Garnish with the Scallion (2) and serve immediately.