Place a large pot over medium heat. Drizzle avocado oil on the bottom of the pot. When oil is warm add onions to the pot. Using a wooden spoon stir the onions cooking until translucent. Add garlic cloves and continue to cook until fragrant. Next, add tomatoes, vegetable stock, oregano, crushed red pepper, and basil to the pot. Bring the mixture to a boil and then cover and reduce heat to medium low. Let the mixture simmer for about 20 minutes.
In a food processor add cream cheese, cheddar cheese, gruyere cheese and jalapeños. Blend until soft and creamy. Spread the cheese mixture on all slices of bread. Taking two slices at a time, place them together to form sandwiches. Spread mayonnaise on the outside of each sandwich.
Place a large pan over medium/high heat. Lightly coat the bottom with avocado oil. When pan is hot place each sandwich face down in the pan. Cook until golden brown on one side. Flip and cook the other side. When both sides are golden brown and cheese is melted, remove the sandwiches from the pan and place on a plate. Cover with tin foil to keep warm.
When soup is done simmering, remove lid and add cream to the pot. Mix well and taste. Add salt and pepper as needed. Using a hand blender, pulse the soup mixture to create a smooth and creamy consistency.
Ladle soup into small bowls and serve with grilled cheese. Enjoy!