Preheat the oven to 180°C / 350°F and line a baking dish with baking paper.
Blend the oat flakes in a blender or food processor until they form a coarse flour.
In a large bowl, whisk the eggs with the Greek yogurt and a pinch of salt until smooth.
In a separate bowl, mix the blended oats with the baking powder.
Add the oat mixture to the yogurt and eggs, stirring until fully combined into a thick, spreadable batter.
Spoon the mixture into the prepared baking dish, filling only half of the pan area and smoothing the top evenly.
Sprinkle a generous layer of seed mix over the surface.
Bake for about 25 minutes at 180°C / 350°F, until lightly golden and set in the centre.
Cool in the tin for 10–15 minutes, then lift out, cool further and slice into squares or bars.