Heat oven to 350°
Line two baking sheets with parchment paper or silicon baking mats
If using frozen butternut squash, cook for half the amount of time on the bag (about 3 minutes) in the microwave. It should be a little bit soft, but not mushy.
Place softened squash into a mesh bag or a clean dish towel and squeeze out as much water as you can - make sure it's cooled enough that the water won't burn your hands (or use rubber gloves)
Roughly chop celery, carrots, onion, and zucchi and place in food processor
Add spinach leaves and garlic cloves to food processor
Process until vegetables are finely chopped
Pour vegetables onto half of one baking sheet and place squeezed butternut squash on the other
Spead cooked black beans out on the other baking sheet
Place both baking sheets in the heated oven and roast for 15 minutes
At the end of the 15 minutes, remove black beans from oven and leave vegetables in for another 15 minutes
Mash black beans with a fork so they are split apart, but leave some bigger pieces for texture
Once vegetables are done roasting, remove from oven and allow to cook for about 10 minutes
Add black beans and vegetables to a large mixing bowl
Whisk eggs
Add almond flour, whisked eggs, salt & pepper to bean and veggie mix
Stir until everything is well combined
Heat avocado oil in larger frying pan over medium heat
Form mixture into patties and palce into hot pan - patties will be soft, if they fall apart a little, push the pieces back together in the pan
Cook over medium heat for 6 - 7 minutes - until burgers are set and bottom is browned and a little crispy. Carefully flip burgers and cook the other side for 6 - 7 minutes
Top with cheese if desired
You can make the mixture ahead of time and store it uncooked in the refrigerator for up to 24 hours before preparing.