Gather all your ingredients: roughly chop the fresh spinach, dice the onion, and mince the garlic.
Add the chopped spinach, diced onion, minced garlic, and vegetable broth into the large slow cooker.
Cover and cook on low for 4 to 6 hours, or on high for about 2 to 3 hours, until the spinach is wilted and the flavors meld, filling your kitchen with a fragrant garlic aroma.
Once cooked, use an immersion blender directly in the slow cooker to blend the mixture until smooth and velvety, or transfer in batches to a blender, blending carefully to avoid splashes.
Stir in the heavy cream to add richness, then warm the mixture gently for about 10 minutes over low heat, stirring occasionally.
Season the soup with salt and pepper to taste, then add a squeeze of fresh lemon juice to brighten the flavors.
If the soup feels too thick, stir in a splash of warm broth or water until it reaches your preferred silky consistency.
Let the soup rest for a few minutes to settle, then ladle into bowls, garnishing with a drizzle of olive oil or fresh herbs if desired, and serve hot.
