Combine wild rice and chicken broth in a saucepan and bring to a boil. Reduce heat, cover, and simmer for 30 minutes. There will still be liquid left in the pan.
1/2 cup wild rice blend, 1 1/2 cups chicken broth
Meanwhile, heat olive oil and butter in a medium stockpot and cook the sausage, browning it on all sides. Transfer sausage to a plate, slice, and set aside.
Add shallots to the oil/butter in the pan and saute for a minute or so, then add sliced mushrooms. Toss to combine and cook over medium heat for 8-10 minutes, stirring occasionally.
Stir in sliced sausage, celery, sage, salt, and pepper. Sprinkle with flour and stir to combine. Add Chardonnay and cook until reduced by half, about 4 minutes or so.
Add vegetable broth as well as the rice and its remaining broth, stir and bring to a boil. Reduce heat and simmer uncovered for 12-15 minutes. Stir in heavy cream and cook for another minute or two until heated through.
3 cups vegetable broth, 4 teaspoons heavy whipping cream
Baby bellas, also called cremini, have more flavor than white button mushrooms and hold their shape in the broth. Buying them presliced saves a lot of prep. Give them room in the pan and let them sit long enough to turn golden, that browning is where the broth gets its color and depth.
If you only have dried sage, use about a third of the amount, since dried herbs are much more concentrated.
Wild rice takes much longer to cook than the rest of the soup, and it keeps absorbing liquid the longer it sits in broth. Giving it a head start in its own pot means it's tender right when the soup is ready, the mushrooms and sausage don't overcook while you wait, and the broth stays brothy instead of being soaked up by the rice.