Preheat oven to 350 degrees. Spray a casserole dish with nonstick cooking spray. In a medium saucepan, melt butter over medium-high heat. Add onion, and cook, stirring occasionally, until onions are translucent, about 3 minutes. Add garlic, and cook and stir for another minute. Whisk in flour to make a roux, cooking and whisking for a couple of minutes to remove raw flour taste. Slowly whisk in vegetable base and water. (Note: you may substitute vegetable stock for vegetable base and water.) And cook for about 7 or so minutes or until sauce is quite thick. Add cream cheese alternative and whisk until melted, followed by shreds and all spices. Check for seasoning, and adjust if necessary. Stir in poblano peppers and then fold sauce into pasta and spoon lightly into prepared dish. Sprinkle topping evenly over the surface, covering completely, and bake, uncovered, for 30 minutes. Let cool for about 15 minutes before serving to allow the sauce to reabsorb back into the pasta.