In a large saucepan, heat 2 tablespoons of oil over medium-high heat. Add 1 diced onion and sauté for 3-5 minutes until translucent. Stir in 2 minced garlic cloves and 1 teaspoon of thyme, cooking for another minute until fragrant.

Introduce 4 cups of broth and 1 cup of apple cider to the pan, followed by 3 cups of diced apples. Bring to a boil, then reduce to a simmer and cook for 20 minutes until apples are tender.

Stir in 1 teaspoon of vanilla extract and 1/4 cup of maple syrup. Add 1 cup of aged cheddar and 1 cup of brie cheese, stirring continuously until melted and creamy, about 5 minutes.

Using an immersion blender, carefully puree the soup until smooth. Season with salt and pepper to taste.

In a medium bowl, mix together 1/4 cup of unsalted butter, 1/2 cup of flour, 1/4 cup of brown sugar, and a pinch of salt until crumbly. Stir in 1 cup of oats and 1/2 cup of chopped walnuts. Spread on a baking sheet and bake at 375°F for 10-20 minutes until golden brown.

Ladle the soup into warm bowls and top with the homemade granola for a delightful contrast in texture.