Prepare all of the ingredients.
In a large stock pot over medium high heat, add oil, leeks and garlic. Cook for 3 minutes then add salt, pepper, potatoes and corn. Cook, while stirring for 3 minutes. Then add jalapenos and chicken broth. Reduce heat to medium and cover. Cook for 20 minutes.
Remove half of chowder to a bowl and blitz with an immersion blender. Return to pot and mix well.
In a small cup, melt butter in microwave (about 30 seconds) then mix in flour with a fork until creamy. Add slurry to pot and mix well. Let cook for 2 minutes then add in heavy cream and continue to stir as you add cheese by the handful. Continue to cook for 3 minutes.
Serve in a shallow bowl and garnish with parsley.