HEAT oil and butter in large saucepan over medium-high heat. Add broccoli, leeks, garlic, bouillon and thyme. Cook, stirring frequently, for 6 minutes. Stir in 1 cup water and baking soda. Bring to a boil; reduce heat to medium. Cover; cook for 20 minutes.
ADD remaining 2 cups water. Increase heat to medium-high. When mixture begins to boil, stir in spinach and cook for 1 minute or until wilted. Cool slightly. Transfer half of soup to blender; add half of evaporated milk. Cover and process until smooth. Transfer to bowl. Repeat with remaining soup and evaporated milk. Return soup to saucepan to heat through. Season to taste with salt and ground black pepper.