Rinse the quinoa thoroughly under cool water. This step is crucial as it removes the bitter coating that can be found on the grains. Transfer the rinsed quinoa to a medium saucepan and add 2 cups of water. Bring it to a boil over medium-high heat.
Once boiling, reduce the heat to low and let it simmer. Cook the quinoa for about 20 minutes, or until it is tender and the water is fully absorbed. When done, remove it from the heat and let it cool. You want it to be fluffy, not mushy.
In a large mixing bowl, combine the cooled quinoa, whisked eggs, Parmesan cheese, scallions, garlic, kosher salt, steamed spinach, and breadcrumbs. Mix everything gently but thoroughly until combined. The mixture should be moist yet hold together well.
Let the mixture sit for at least 5 minutes. This resting period allows the breadcrumbs to absorb some moisture, making it easier to form patties. The mixture should not be too runny; you want it to be sticky enough to hold its shape.
Using your hands, form the mixture into patties, about 1/4 cup each. You should be able to get around 12 patties. Place them on a plate or a baking sheet lined with parchment paper.
In a large non-stick skillet, heat olive oil over medium-low heat. Once the oil is hot, add the patties in batches, being careful not to overcrowd the pan. Cover the skillet with a lid to help the patties cook evenly.
Cook the patties for about 8 to 10 minutes on each side, or until they are golden brown and crispy. You can gently flip them with a spatula. Look for a nice, golden crust on the outside.
Once cooked, remove the patties and place them on a paper towel-lined plate to absorb any excess oil. This helps keep them crispy and not greasy.
Serve the patties warm. They can be enjoyed on their own, with a side salad, or your favorite dipping sauce. The flavors will continue to improve as they sit!