Prepare the vegetables: Dice the onions into small pieces. Wash the leeks and slice the white parts into large coin size pieces. With a knife remove the skin of the pumpkin. It is easier if you do this by section. Then cut each section into large cubes.
Pour the olive oil in a large pot over a medium heat. When the oil is hot, add the onions. Continue to cook the onions for a few minutes until the onions become translucent.
Add the leeks and continue to cook about five minutes to soften them up and let out flavor.
Add the pumpkin into the pot and continue to cook up to 5 minutes, stirring periodically.
Add the white wine and let it cook and bubble for a few minutes.
Add roasted garlic (without skins), thyme and, if you are using them, bouillon cubes. Let simmer for a minute or two.
Add the vegetable broth (or water if you added the bouillon cubes above). Bring to a boil and then reduce heat and leave to simmer covered for about 30 minutes.
Remove the pot from the heat. If you have a hand blender, use it to blend the soup into a smooth consistency. If you do not have a hand blender, put portions of the soup into a blender and mix until smooth. Continue until all soup is blended.
Add the salt and pepper. Taste and adjust seasoning.
Serve in bowls and, if you like, add some additional sauteed leeks on top as shown in the featured photo. Enjoy!