Return the onion/garlic mixture and add veg broth bringing it to a gentle simmer before reducing to lowest heat again. Add the green curry paste (using the back of a wooden spoon to break it up and integrate). Add the ginger and the coconut milk, stirring to combine.
Taste the curry and make any flavor/heat adjustments. You can also make any liquid adjustments as desired (a little more coconut milk, broth, etc).
While things are still warm, add the spinach - one large handful at a time - mixing to integrate until all has been added and the spinach is wilted.
Serve right away with accompaniments of choice and top with a sprinkle of nutritional yeast and/or cilantro as desired.
Notes
What kind of spice/heat level can I expect? I recommend starting with 2 tsp of Mae Ploy - a quantity that will allow you to feel the heat with room to grow (it's not as easy going in the other direction if you use too much at first) - be careful with this paste - you don't want to sample it directly on your tongue, treat it like a hot pepper and allow it to release its heat into the food before tasting. Is Mae Ploy green curry paste vegan? It is not (it contains shrimp paste). For flavor profile, I suggest Maesri Green Curry Paste or Aroy-D Green Curry Paste in its place. If you don't have access to an Asian market, both are available on Amazon. There are also a number of homemade vegan green curry paste recipes available online if you want to go that route. What's the deal with nutritional yeast? Typically sold in flake form (looks a bit like a shaker of parm cheese), nutritional yeast adds yummy flavor and nutrients to food. A source of B vitamins -- notably fortified with B12 important for vegans. I like its nutty (mildly hoppy) taste and many find it has a flavor reminiscent of cheese. Give it a try!
Recipe by Inspired Edibles at https://www.inspirededibles.ca/2018/01/thai-green-curry-with-chickpeas-cauliflower-spinach.html