Preheat your oven to 375°F (190°C) and prepare a muffin tin by greasing it or lining it with muffin liners.

In a large mixing bowl, whisk together the all-purpose flour, ground flaxseed, baking powder, salt, garlic powder, and optional red pepper flakes.

In a separate bowl, beat the Greek yogurt and large eggs until smooth and creamy.

Gently fold the wet ingredients into the dry mixture using a spatula until just combined.

Stir in the wilted and drained spinach, chopped chives, and your choice of cheddar cheese.

Spoon the biscuit mixture evenly into the prepared muffin tins, filling each cup about three-quarters full.

Place the muffin tin in the preheated oven and bake for 20 to 22 minutes until golden brown.

Allow your biscuits to cool in the tin for 5 minutes before transferring them to a wire rack.