Adjust rack to top position and preheat oven to 450 degrees. Wash and dry all produce. In a large microwave-safe bowl, combine stock concentrates and 4 cups water (7 cups for 4 servings); microwave until hot, 3-5 minutes. Thinly slice garlic. Halve, peel, and mince shallot. Zest and quarter lemon. Pick sage leaves from stems; thinly slice leaves.

Heat a drizzle of oil in a large pan over medium heat. Add garlic and shallot. Cook until softened, 1-2 minutes. Add rice; stir until translucent, 1-2 minutes. Add ½ cup stock; stir until liquid has mostly absorbed. Repeat with remaining stock—adding ½ cup at a time and stirring until liquid has mostly absorbed—until rice is al dente and mixture is creamy, 25-30 minutes.

While risotto cooks, toss squash on a baking sheet with a drizzle of oil and a pinch of salt and pepper. Roast until browned and tender, 20-25 minutes.

Meanwhile, pat scallops dry with paper towels; season generously all over with salt and pepper. Heat a large drizzle of oil in a second large pan over medium-high heat. Add scallops and cook until browned and cooked through, 3-5 minutes per side. Turn off heat. Remove scallops from pan and set aside, covered. Wipe out pan.

Melt 2 TBSP butter (3 TBSP for 4 servings) in pan used for scallops over medium heat. Cook, stirring, until butter is foamy and flecked with amber brown bits, 2-3 minutes. Stir in sage leaves and a squeeze of lemon juice. Turn off heat; carefully transfer to a small bowl. Once risotto is done, stir in roasted squash, lemon zest, Parmesan, 1 TBSP butter, and a squeeze of lemon juice.

Taste and season risotto with salt, pepper, and more lemon juice if desired. Divide between bowls and top with scallops. Drizzle with brown butter. Serve with any remaining lemon wedges on the side.