Halve, peel, and finely chop the onion. Slice the mushrooms. Thinly slice the garlic. Strip the thyme leaves off the sprig, then finely chop. Remove the sausage from the casings.

Heat 1 tablespoon olive oil in a large pan over medium heat. Add the sausage and onion to the pan and cook, breaking up the pieces, for about 3-4 minutes, until sausage is browned but not yet cooked through.

Add the mushrooms, half the garlic, and thyme to the pan with the sausage and cook, tossing, 4-5 minutes, until softened. Add the fregula sarda and stir for about 1 minute to lightly toast. Add 2 cups water and the stock concentrate and bring to a boil. Reduce to a simmer, and cook for abour 15 minutes, until fregula sarda is tender with a bit of bite to it.

Meanwhile, heat 1 tablespoon olive oil in a medium pan over medium heat. Add the remaining garlic and cook for 30 seconds, until fragrant, Add the spinach and cook, tossing, about 2-3 minutes, until wilted. Add a splash of water, if necessary. Season with salt and pepper.

Stir the Parmesan into the fregula sarda mixture and serve in bowls topped with the wilted spinach.