01 - Preheat oven to 375°F. Toss bread cubes with olive oil, garlic powder, dried thyme, and a pinch of salt. Spread on a baking sheet and toast for 12 to 15 minutes, tossing halfway through, until golden and crisp. Set aside.
02 - In a large pot, melt butter over medium heat. Add onion and celery; cook for 5 minutes, until softened. Stir in garlic and cook for 1 minute more until fragrant.
03 - Add broccoli and potato to the pot; cook for 2 to 3 minutes, stirring frequently. Season with salt, pepper, and nutmeg.
04 - Pour in vegetable broth. Bring to a boil, then reduce heat, cover, and simmer for 15 to 20 minutes, until vegetables are completely tender.
05 - Remove pot from heat. Using an immersion blender, purée soup until smooth and creamy. Alternatively, transfer to a countertop blender in batches.
06 - Return pot to low heat. Stir in milk and shredded cheddar; cook, stirring constantly, until cheese is completely melted and soup is heated through. Do not allow to boil.
07 - Taste and adjust seasoning with additional salt and pepper as needed. Serve hot, topped with homemade croutons and an extra sprinkle of cheddar if desired.