Place a large pot on medium high heat. Add the unsalted butter and olive oil. When it starts to smoke add in the carrots, celery and onion. Turn the heat down. Let cook for about 8-10 minutes. Add 1/2 Tbsp. salt onto the vegetables while cooking. You can put a lid on this to help sweat the vegetables, but make sure you keep an eye on them. Add in the curry and tumeric powder. Give a stir and let cook for another 4 minutes.
Add in the roasted pumpkin puree, the drained potatoes and the 6 cups of cold water. Give a stir. Bring to a boil and let simmer for 45 minutes or until the potatoes mash easily with a fork.
You can puree with a wand at this point or let cool for 20 minutes and puree in a food processor.
With a soup ladle or spoon, check the thickness of the soup. If it is too thick, add a little more water. You want to create a nice soup, not a porridge. Taste and season with salt and pepper. I like to add a little heavy cream to give the soup an extra depth of flavor. This is optional.
Recipe Notes: You could use any type of squash or pumpkin for this soup. Just cut the squash or pumpkin in half or quarters, depending on the size. Remove the seeds and innards. Roast on a sheet pan in a 350º oven for an hour or till soft. Let cool, scoop out the flesh. This could be done a day before. I often freeze the flesh and let thaw out the night before in the fridge. It is a great way to enjoy fall flavors in the dead of winter.
You could also use fresh fresh Tumeric. You only need a small finger of the Tumeric, with edge of a spoon rub the skin off and finely grate onto a plate. Add the grated Tumeric with the curry powder. Your hands will be stained a little.
This is a great evening meal paired with a green salad.