Heat a nonstick skillet over medium-low heat and add the chorizo. Using a wooden spoon, break it apart as it cooks until browned and crumbled, about 5 to 6 minutes. Transfer the cooked chorizo to a paper-towel lined plate to drain excess grease.

Heat a saucepan over medium heat and add olive oil and butter. Stir in the diced jalapenos, diced onion, and minced garlic. Season with salt and black pepper. Cook until the onions soften, about 5 to 6 minutes.

Slowly stream in 1 cup of the half and half while whisking continuously. In a small bowl, whisk the remaining ½ cup half and half with cornstarch until smooth to create a slurry. Stir the slurry into the saucepan and cook for about 1 minute until the mixture thickens. Reduce heat to low.

Add grated cheddar and Monterey Jack cheeses in small handfuls, stirring constantly until the cheese melts completely. Then stir in the pumpkin puree until fully combined, creating a creamy queso mixture.

Transfer the queso mixture to a crockpot set on low, or a serving bowl if immediate consumption is intended. Spoon the cooked chorizo on top, then garnish with roasted pepitas, fresh cilantro, sliced jalapeno peppers, and a sprinkle of cotija cheese. Serve immediately with tortilla chips.