Cut ends of squash off and slice down the middle so you have two halves. Using the narrowest setting on your mandolin, slice the squash into long, flat strips.
In a large pan, heat oil over medium heat. Add onion and a pinch of salt and sauté for about 5 minutes, until nearly translucent. Add garlic and sauté until fragrant.
Add ground chicken to onion and garlic and sauté until chicken is cooked all the way through.
Squeeze all the excess water out of the spinach, then add chicken, spinach, salt, pepper, and egg whites to a food processor or blender and puree until mixture reaches desired.
Assemble the ravioli by just barely overlapping two strips of squash. Do the same over the middle of the first two strips, but perpendicular, creating a cross or “+” shape.
Spoon filling in the center of the cross, then bring the ends of the strips together, overlapping each other.Secure with a toothpick.
Before serving, steam raviolis for about 4 minutes, or until squash is tender and inside is warm.
