Heat the large pot over medium heat and drizzle in the olive oil. Add the sliced fennel and cook, stirring occasionally, until it turns translucent and begins to soften, about 8 minutes, releasing a fragrant aroma.
Add the minced garlic to the fennel and cook for another minute, stirring gently until fragrant and slightly golden, blending into the fennel’s aroma.
Pour in the white wine (if using) and let it simmer until reduced by half, about 4 minutes, which concentrates the flavors and adds a subtle acidity to the broth.
Pour in the fish or vegetable broth, then add lemon zest and juice. Bring the mixture to a gentle simmer, allowing the fennel to continue softening and the flavors to meld, about 10 minutes.
Gently nestle the salmon chunks into the simmering broth, skinless side up. Cover the pot and cook for about 8-10 minutes, or until the salmon flakes easily with a fork and the fennel is tender.
Taste the broth and season with salt and freshly ground pepper as needed, adjusting the acidity with additional lemon if desired.
Carefully ladle the stew into bowls, ensuring some of the tender fennel and flaky salmon go with each serving. Garnish with a fresh lemon wedge if you like a bright finish.
