Add the tofu, garlic cloves, lemon juice, nutritional yeast, mustard, salt and pepper to a high-speed blender or food processor.
Blend for 1-2 minutes until smooth. Add water a little bit at a time until you get a creamy consistency.
In the meantime, thaw the spinach in the microwave and slightly press to remove any excess water.
Add the spinach and sunflower seeds to the food processor and pulse a few times to incorporate everything evenly. You still want some chunks of spinach and sunflower seeds left.
Give it a taste and - if necessary - add more salt and pepper to taste.