Slice the zucchini in half and then into one inch pieces.
Peel the potatoes and chop into one inch pieces also.
Remove the stems from the mushrooms and quarter them.
In a large stock pot over medium heat, add the butter & olive oil.
Add in all of the vegetables
Season with salt, pepper & red pepper flakes.
Sauté the veggies, stirring occasionally for about 10 minutes or until they just begin to soften.
Add in about 3 cups of vegetable stock (just enough to cover the vegetables)
Increase the heat to medium high and bring to a boil.
When the potatoes are fork tender, turn off the heat
Blend and puree the mixture either in a blender or use a submersion blender
Add in the Parmesan cheese and stir until it is melted.
Transfer to soup bowls and serve immediately
Notes
Nutrition Info is approximate* Tip on how to clean leeks - Remove the dark green leaves from the top of the leeks, slice in half and run them under cold water to remove the dirt between the layers