Heat the olive oil in a large pot or Dutch oven over medium heat.
Add the chopped onions, cover, and cook until softened and fragrant, about 5 minutes.
Stir in the sliced mushrooms, dried savory, and vegetable broth. Increase the heat and bring the mixture to a boil.
Reduce the heat to low.
Add the drained and rinsed Great Northern beans, and season generously with salt and pepper.
Let the soup simmer gently for about 10 minutes to allow the flavors to meld together.
For a creamy texture, use an immersion blender to partially puree the soup directly in the pot, leaving some chunks for texture. Alternatively, carefully transfer about 2 cups (480 ml) of the soup to a standard blender, puree until smooth, and stir it back into the pot.
Continue to simmer for another 5 minutes, tasting and adjusting the seasonings as needed.
To serve, ladle the hot soup into bowls and garnish with a sprinkle of fresh parsley.
Don't be afraid to swap the herbs! Fresh dill or thyme works beautifully as a substitute for the savory and parsley.