In a skillet, melt 2 Tbsp. butter and sauté ½ large onion, 1 large red pepper, 2 cloves garlic, 4 oz. mushrooms, 1 cup carrots, 2 lbs. fresh asparagus, ¼ tsp. salt, & ¼ tsp. pepper for about 8 minutes.
Add sautéed vegetables to slow cooker along with 8 cups vegetable broth, 2 cups water, ½ tsp. dry dill, and ½ tsp. dry tarragon.
For slow cooker: set to low and cook for 6-8 hours.For pressure cooker: cook for 35 minutes.
Take out ½ cup broth from cooker when finished and whisk ½ cup all purpose flour into broth. Pour floured broth to cook along with 4 cups half & half . Keep warm and serve.