Melt the butter and the oil in a deep saucepan or cast-iron pot over low-medium heat. Once hot, add the sliced onions and sauté for 3-5 minutes.
Season with a pinch of salt and continue cooking the onions for 30-35 minutes, stirring regularly, until the onions are golden brown. Be patient, you want to caramelize the onions slowly.
Next, add the minced garlic and cook for one more minute.
Sprinkle the flour over the onions and stir to coat.
Deglaze the pot with the white wine and increase the heat to medium. Cook for about 3 minutes.
Pour in the vegetable broth, ground black pepper, and salt. Cover the pot with a lid and let it simmer for about 30 minutes. Taste and adjust seasoning if needed.
Preheat your oven with the broiler on. Divide the soup between 4 small bowls or mini cocottes. Top each bowl with a thick slice of bread and drizzle with 2-3 tablespoons of vegan cheese sauce.
Place under the broiler for 1-2 minutes or until the bread is toasted. Top with chopped scallions and serve immediately!
Drain the raw cashews and transfer them to a blender. Add all the other ingredients and blend for 10-15 seconds or until smooth.
Transfer to a small saucepan and heat over low-medium heat, constantly whisking until it thickens. Remove from heat and use immediately.
