Dry roast 2 tbsp of pine nuts in a small fry pan under a medium heat for 3 to 4 minutes, make sure to mix them continuously so they cook evenly and don´t burn, then set aside
Heat a large pan with a medium heat, add in a ¼ cup of cold water and 300 grams / 10 ounces of bagged spinach, place a lid on the pan and steam for 4 minutes, then remove the lid and turn off the heat, mix the spinach so it´s all welted, transfer the spinach to a sieve with a bowl underneath and using a spoon push down on the spinach to remove any of the excess water, then add the spinach to a cutting board and finely chop as best as you can
Heat a frying pan with a medium heat and pour in 2 tbsp extra virgin olive oil, 2 minutes later add in a ¼ cup of finely diced onions and 2 minced garlics, mix with the olive oil, 3 minutes later add the spinach into the pan, the toasted pine nuts and season generously with sea salt & black pepper, mix together until well combined, then add in a ¼ cup of all-purpose flour, a little at a time and mix together, once the flour is incorporated, add in a ¼ cup of milk, again, a little at a time while you continue to mix, once all the milk has been incorporated compact the mixture, then add to a bowl, cover with seran wrap and add to freezer for 10 minutes
Meanwhile, add a generous portion of plain breadcrumbs to a bowl, season with sea salt and mix together, in another bowl crack in 1 large egg, pour in 1 tbsp of milk, season with sea salt and whisk together
After 10 minutes, grab the spinach mixture and start forming the croquettes, using a spoon grab some of the mixture and shape it into the form of an egg, then dip it in the egg wash and then cover completely with breadcrumbs, you should get about 10 croquettes from this recipe
Heat a small fry pan with a medium-high heat and pour in ½ cup virgin olive oil, after 3 minutes add the croquettes into the hot oil, cook in batches to not over-crowd the pan, after 30 seconds flip the croquettes and cook for another 30 seconds, then remove from the pan and transfer to a plate with paper towels, once they are all cooked they are ready to be served, enjoy!