Melt 2 tablespoons butter with 2 tablespoons olive oil in a large Dutch oven over medium-high heat. Add mushrooms and stir to coat then push into an even layer (not all mushrooms will be touching the bottom). Cook undisturbed until they turn deeply golden brown on the bottom, about 10 minutes. Add Worcestershire and continue to cook, stirring occasionally until the mushrooms are dark (but not burnt) and very dry, about 8 more minutes. Transfer to a bowl; don’t wipe out pot.: The pan will become fragrant with an earthy aroma as the mushrooms begin to brown, and you will hear a soft sizzle that quiets when the juices reduce. Pushing them into an even layer encourages Maillard reaction, giving deep golden color and concentrated flavor. When they release moisture, resist stirring too often, letting the bottom caramelize; then the added Worcestershire will deglaze and intensify the savory notes. A key sensory cue is that the mushrooms will smell nutty and look glossy before turning dry. If you stir constantly you will steam them instead of browning, so avoid that. Watch the heat to prevent spots from burning, and transfer them once they look dry and richly colored so they do not overcook in the pot.
Reduce heat to medium and melt 2 tablespoons butter with 2 tablespoons olive oil. Add onions, carrots and celery and sauté until the onions are tender, 6-8 minutes. Add garlic, and all seasonings and cook one additional minute. Add flour and cook one additional minute, while stirring (it will be thick).: The softened onion , carrots , and celery will release a sweet, aromatic steam and the pan will sound lively with gentle bubbling. This is where the flavor base forms, so allow the vegetables to sweat and turn translucent, not brown. Adding the garlic and dried herbs briefly releases bright aromatic oils without permitting burning. When you stir in the flour , it should coat the vegetables and smell toasty rather than raw after a minute of cooking. This step thickens the soup so the final texture is velvety. If the mixture smells floury, cook a bit longer to eliminate that raw taste. Stir constantly while the flour cooks to avoid lumps.
Add the mushrooms back to the pot followed by the wild rice blend and beef base. Add the water while stirring to scrape up the bits from the bottom of the pan.: Returning the browned mushrooms and adding the grain and beef base builds layers of flavor. When you add the water , use a wooden spoon to scrape the fond from the bottom, those brown bits dissolve and enrich the broth. You will see the liquid pick up a deep brown color and the aroma will shift to a concentrated, meaty scent. Stirring as you add water ensures the rice is distributed evenly and the bouillon dissolves. If you do not scrape well, some of that flavor will remain stuck and the soup will be less complex, so take a moment to deglaze thoroughly.
Cover and bring to a boil, then reduce heat to LOW. Simmer, covered, until rice is tender, 45-60 minutes, stirring occasionally and replacing the lid. Stir more often after 30 minutes so the bottom doesn’t stick and burn as the soup reduces/thickens quite a bit.: As the pot comes to a boil the steam will smell savory and the surface may ripple gently. Lowering to low ensures a steady, gentle simmer where the wild rice slowly hydrates and swells. You will notice the broth gradually darkening and the aroma becoming deeper. After about 30 minutes, the soup will visibly reduce and thicken, so stir more often to prevent sticking and check the rice for tenderness. A sign the rice is done is when the grains are tender with a slight bite, not chalky. Avoid turning the heat too high to speed things up, because vigorous boiling can toughen rice and cause the bottom to scorch.
Stir in half and half and balsamic vinegar followed by lemon juice to taste. Season with salt and pepper to taste. Dig in!: When you add the half and half , the aroma will become creamier and the surface smooth out; the soup should look glossy and coat a spoon. The small splash of balsamic brightens the deep flavors and the lemon juice lifts the bowl with freshness. After seasoning with salt and pepper , taste and adjust carefully because the concentrated broth can become salty quickly. If the dairy cools the pot too much, gently rewarm on low while stirring. Common errors here are adding too much acid or salt at once; add gradually and taste between additions.
