Step 1

Heat 2 Tbsp. oil in a medium Dutch oven over medium-high. Cook mushrooms, tossing occasionally, until browned and crisp, 6–8 minutes. Season with salt; transfer to a plate. Let pot cool 2 minutes.

Step 2

Set pot over medium heat and pour in remaining 3 Tbsp. oil. Cook onion and shallots, stirring occasionally, until softened and starting to brown, 6–8 minutes. Add sliced garlic and butter; cook, stirring often, until garlic is softened and starting to brown, about 2 minutes. Add wine; simmer, stirring once, until reduced by half, about 5 minutes. Add farro, miso, and 6 cups water. Bring to a boil, stirring to dissolve miso. Reduce heat and simmer, uncovered, stirring once or twice, until farro is halfway cooked, about 20 minutes.

Step 3

Taste broth and season with salt. Add squash (submerge the best you can), cover, and cook until tender, about 30 minutes. Add mushrooms; cook just until heated through, about 2 minutes.

Step 4

Ladle stew into bowls; top with parsley, lemon zest, and chopped garlic.