Heat large pot of boiling water. Add zucchini and yellow squash rounds, boil for 3 minutes, drain and set aside.
Add butter to pot and melt over med heat,when butter is hot saut'e onions till tender.
meanwhile transfer cooked zucchini and squase to food processor, puree them until smooth pour the pureed zucchini & squash back into pot with the onions, add soup base and stir it in with the onions and zucchini and squash.
Finally, add the half & half and enough chicken broth to make the soup the consistency that you want.