Heat olive oil in a large soup pot. Sauté onion, carrot, garlic and celery in the olive oil until the onion begins to soften. Stir in the oregano leaves. Pour in vegetable broth. Add corn, red potatoes, diced tomatoes and green chiles. Bring soup to a boil and then lower heat and simmer for about 20 minutes until the potatoes have softened but still hold their shape.

Meanwhile, in a large sauce pan, melt butter and stir in flour. Stir flour/butter mixture over the heat until the flour takes on a light brown color. Whisk in milk and continue whisking until mixture starts to thicken. Mine thickened pretty quickly, so watch your pan at this step. Add more milk if necessary.

Add flour/butter mixture to the soup, whisking it in and continuing to whisk until the soup thickens.

Add cheese to the hot soup by handfuls just before serving. Thin soup with additional milk or vegetable broth as necessary.

Garnish with chopped cilantro.