In a saucepan, saute chopped onion in 4 Tablespoons of Olive Oil over medium heat for about 4 minutes or until translucent.
Add minced garlic to saucepan and saute for 1 minute. Add basil, sage and black pepper to saucepan and stir to combine.
Add onion-garlic mixture to your Crock Pot or slow cooker.
Add chicken stock, chopped apples and chopped butternut squash to Crock Pot and set timer to high for four hours.
When soup is ready, unplug Crock Pot as a safety precaution. Using an immersion blender, immerse blender in Crock Pot and pulse for several minutes until soup is pureed. Alternatively, remove soup from Crock Pot and blend in small batches in your blender.
Ladle soup into bowls and top with sliced swiss cheese. Place under oven broiler for 2 minutes or in microwave for about 45 seconds to melt the cheese. Serve immediately.