I made some sort of fennel & lemon soup over the holidays, and I had some fennel kicking around in my fridge for a couple weeks now so I decided to throw something similar together. I didn't measure anything really....just roughly and added whatever I thought would go together. It was astoundingly delicious AND filling! Plus - I have tons leftover in a big pot in the fridge

3 small cloves garlic
1 small shallot
1/2 fennel bulb (generous one half...)
2-3 celery stalks
1 lemon (peeled, seeds removed)
1/2 yellow pepper
(I had a small piece of a zucchini in the fridge as well so I tossed that in too)
about an inch of daikon radish, peeled and chopped roughly
Some raw apple cider vinegar
LOTS of cold water
Optional garnish - parsley
Toss it all in the food processor! I blended the garlic and shallot first, then kind of threw everything else in. The daikon was a last minute addition, so in retrospect it probably would have made more sense to put it in at the start as it could take longer blending easily. Blend until pieces are small, but not until the mixture gets like a puree/pate or too smooth. I suppose you could alter this if you prefer creamy soups, and blend more and add just a small amount of water, but I prefer more brothy soups.
I emptied out the food processor into a big pot and added a bunch of water. I have an average sized food processor, so I filled it about half way a couple times with cold water and added it in. Again, I guess it doesn't really matter, so just add water until desired consistency! I added a splash of apple cider vinegar, and realized the flavours went really well together after a taste, so I added a few more splashes to the mix, to taste. Possibly about 1/3-1/2 a cup of it in the end? The water and vinegar can really be up to you and what kind of soup/combo you think tastes best.
After scooping some into a personal bowl, I added a pinch of parsley on top. Soooo good.
Adjust flavours to your taste and enjoy!