In a medium pot, start by cooking the onion with a good pinch of salt and pepper on medium-high heat for about 3 minutes or until softened. Then, add the potatoes, garlic, thyme, lemon zest and red pepper flakes (if using). Cook for 1-2 minutes while stirring.
Then, add the vegetable broth, stir and cover. Bring to a gentle boil, then cook on medium heat for about 6-7 minutes or until the potatoes are about halfway cooked through (cooking time will depend of the size of the diced potatoes). Do not completely cook the potatoes at this point.
Add the spinach and chives, stir, cover and cook for about 2-3 more minutes or until the potatoes are just cooked through but still firm (do not let the potatoes become mushy, you do not want the potatoes to fall apart!). Taste and adjust the seasoning.
Serve warm topped with more fresh chives and red pepper flakes with a side of bread. Enjoy!