Preheat the oven to 350°F (175°C) and lightly grease an 8×8-inch baking dish with oil or butter.
Add Greek yogurt to a large mixing bowl and whisk until smooth and creamy.
Crack the eggs into the bowl and whisk until fully incorporated with the yogurt.
Pour in maple syrup or honey and mix well to combine the sweetness evenly.
Stir in vanilla extract and a pinch of salt for flavor balance.
Sprinkle the cornstarch into the mixture and whisk thoroughly to eliminate lumps.
Gently fold the mixed berries into the yogurt batter without crushing them.
Pour the mixture into the prepared baking dish and spread it evenly.
Add a few extra berries on top for color and texture.
Bake in the oven for about 35–40 minutes until the edges are lightly golden and the center is set.
Remove from the oven and allow the bake to cool for 10–15 minutes before slicing.
Serve warm or chilled depending on your preference.