Prepare a mini muffin pan with cooking spray or line with mini cupcake liners; set aside.
Heat olive oil in a large skillet over medium-high heat.
Add onions and sauté for about 2 minutes, until onions are slightly softened and start becoming translucent in color.
Add spinach and sauté for one minute. Remove onions and spinach from heat and let cool.
In a large bowl, whisk together eggs, almond milk, cheese, chives, thyme, salt and pepper. Add in the onions and spinach and whisk until ingredients are well blended.
Pour or spoon the egg mixture into each open mini muffin tin.
Bake at 350°F degrees for 18-20 minutes, just until the center of the frittatas are set and no longer jiggly.
Notes
Makes approximately 20-24 mini frittatas.Storage: store in an airtight container for up to 4-5 days.Make ahead: These can be made the night before, and refrigerated in an airtight container overnight.To reheat: place frittatas on a baking sheet and reheat at 325° degrees for about 5 minutes, or place in an air fryer basket and air fry at 300°F for 2 minutes.