Cut broccoli and cauliflower into bite size pieces.Boil broccoli and cauliflower directly in the chicken stock until al dente, about 10 minutes.In a large saucepan, melt 2 tablespoons of butter and add onion. Saute onions until soft and translucent.Add 2 more tablespoons of butter and the flour 1 tablespoon at a time, to make a rue.Once the mixture has created a rue (a paste like consistency) add milk/cream slowly to mixture slowly, whisking while mixture together.Split the broccoli/cauliflower mix in half. Take half of the mixture to a blender and puree until smooth. Pour mixture into the cream-rue mixture, add the remainder of the whole florets to the soup.Turn the stove top to down to low and allow the soup to simmer for at least 15 minutes.Stir soup every 5 minutes or so while it simmers to make sure the cream does not burn to the bottom of the pan.Taste and add more salt, pepper, garlic powder, seasoning salt as desired.