Preheat oven to 375°F (190°C). Line a baking sheet or grease a muffin tin.
Mix wet base: Whisk yogurt and eggs until smooth.
Add dry ingredients: Stir in flour, flaxseed, baking powder, salt, garlic powder, and red pepper flakes until just combined.
Fold in your mix-ins of choice (ham & cheese OR Mediterranean).
Scoop dough: Use ⅓ cup per biscuit. Place on sheet or fill muffin wells.
Top & Bake: Sprinkle reserved cheese or feta. Bake 25 mins until golden and firm.
Cool 10 mins before serving or storing.