In a large Dutch oven, combine 2 tablespoons of butter and 1 tablespoon of canola oil over medium-high heat. Allow the butter to melt completely while foaming but not browning, about 2 minutes. Once melted, add approximately 3 cups of chopped onion, reducing the heat to medium-low. Sauté for 6-7 minutes until the onions are softened and translucent.

Stir in about 6 cups of coarsely chopped green cabbage to the softened onions. Cook for an additional 2-3 minutes, stirring occasionally, until the cabbage wilts and slightly reduces in volume.

Add in diced red potatoes and pour in 6 cups of chicken or vegetable broth, stirring gently to combine all ingredients. Bring the mixture to a rapid boil, then reduce the heat to a simmer and let it cook uncovered for 12-15 minutes until the potatoes are fork-tender.

Prepare a thickening slurry by mixing 5 tablespoons of all-purpose flour with 1/2 cup of the soup liquid until smooth, then whisk in 2 cups of half-and-half.

Carefully incorporate the flour and half-and-half mixture back into the simmering soup. Stir thoroughly and add optional caraway seeds if desired.

Once thickened, add 2 tablespoons of Dijon mustard, 1 tablespoon of Worcestershire sauce, and 1/2 teaspoon of hot sauce. Adjust seasoning with salt and black pepper to taste.

Remove the soup from heat and let it sit briefly before serving. Garnish each bowl with freshly chopped parsley, if desired, and enjoy hot.