Cook chorizo in a skillet over medium high heat until fully cooked, breaking it apart. Set aside.
In a 3 or 4 quart slow cooker, combine 3/4 of the cooked chorizo (save the remaining 1/4 for garnish), onions, cream cheese, Monterey Jack cheese, 1/2 cup of the evaporated milk, and the diced green chiles. Cook on LOW for 1 to 1.5 hours, or until evenly melted and warm. Stir every 20 or 30 minutes for even cooking.
After about 1 hour, check on the consistency. If you want the queso to be thinner, add more evaporated milk (heat up the milk in the microwave oven first), and stir until desired consistency. If needed, season with salt and pepper to taste.
To serve, garnish with the remaining chorizo, chopped cilantro, diced tomatoes, and jalapeños. Serve with chips. Enjoy!