Pour oil into a large pot and place over medium heat.
Add onion, carrot and celery and sauté for 4 to 5 minutes. Season with salt and pepper.
Add garlic, cauliflower and herbs and continue to sauté for an additional 3 to 4 minutes.
Add 3 cups of the stock to the pot and simmer for about 20 minutes or until cauliflower is tender. Season with salt and pepper.
Strain half the vegetables from the pot and set aside.
Pour remaining mixture into a blender and blend until smooth, adding remaining stock, as needed, until a thick consistency has been achieved.
Pour mixture back to the pot and stir in strained vegetables. Adjust seasonings. Simmer for 2 to 3 minutes before removing from heat.
For seasoned oyster crackers: Melt butter in a skillet over medium heat. Add oyster crackers and stir to coat in butter. Add remaining ingredients and continue to sauté for about 2 minutes. Remove from heat and allow crackers to cool and dry.
To serve: Pour chowder into bowls and top with oyster crackers. Garnish with strips of bacon, if using. Serve.