Blanch the collard greens. Bring a large pot of salted water to a boil. Cook the collards in the boiling water for 2 minutes, then transfer to a large bowl full of ice water immediately. Shock in the ice water, then drain between layers of paper towels - gently pressing to remove the water.
In a large bowl, whisk together the sour cream, heavy cream, flour, chili garlic sauce, and salt & pepper to taste.
Place a large pot on medium heat. Add the olive oil. Add the spicy Italian sausage (you can switch out the hot italian sausage to mild if you don't like the heat) & the chopped red onion. Season with salt & pepper to taste. Saute, stirring often, until the sausage is cooked through. Stir in the garlic & cook for another minute.
Add the cream mixture. Stir in the collard greens, combining well. Cover & cook on medium heat for about 30 minutes, stirring a couple of times. Serve hot.