Cream of Asparagus Soup with Gruyère

I've made this dozens of times.  First time with Gruyère. 

Ingredients:

1/2 stick unsalted butter
1/2 onion, chopped
1 clove garlic, crushed
Salt and freshly ground black pepper
2 pounds asparagus, ends trimmed and cut into 1-inch a pieces
6 cups chicken stock
1 pint cream, room temperature
1teaspoon rosemary
1 cup shredded Gruyère cheese

Directions:

Melt butter in a large saucepan over medium-high heat. Add onion and garlic, and saute 5 minutes. Season with salt and pepper. Add asparagus and saute another 4 minutes. Add the chicken stock and bring to a boil. Reduce to simmer and cook for 30 minutes, until asparagus is very tender. *Carefully transfer to a blender and puree until smooth. Return to saucepan, stir in sour cream and season with salt and pepper, to taste. Transfer to serving bowls. Dust with paprika and serve.

*When blending hot liquids: Remove liquid from the heat and allow to cool for at least 5 minutes. Transfer liquid to a blender or food processor and fill it no more than halfway. If using a blender, release one corner of the lid. This prevents the vacuum effect that creates heat explosions. Place a towel over the top of the machine, pulse a few times then process on high speed until smooth.