I think the grapefruit juice sounds like an odd addition...but I've never seen or tried a recipe like this so who knows...maybe it's great! I'm thinking the addition of the grapefruit may keep the avocado from turning brown? Here's another variation of homemade cream of soup that I have tried and it's quite good!
Cream of Mushroom Soup
Makes 8 Servings
1/4 cup butter
1 pound fresh mushrooms, sliced
1/4 cup all-purpose flour
3 cans chicken broth, low or no sodium
1 cube beef bouillon
1 cup evaporated skim milk (or if calories aren't a concern, use heavy cream)
Salt and pepper to taste
In a large saucepan, melt butter over medium heat. Cook mushrooms in butter 5 minutes. Sprinkle flour over mushrooms. Pour in broth, a little at a time, stirring constantly. Stir in bouillon cube. Bring to a boil, then remove from heat and stir in evaporated skim milk. Heat through, without boiling. Serve.
If you are persistent, you will reach your goal. If you are consistent, you will keep it.