Preheat the oven to 350F.
In a medium mixing bowl add in plain greek yogurt, crack in an egg, add the maple syrup and vanilla extract and whisk until smooth.
Using your fingers or the back of a large spoon, press down on the middle of your slices of bread to create a little pool in the center for the custard to fill.
Pour the custard into the bread pools, dividing the mixture evenly between the two slices.
Drop your chosen toppings into the custard such as berries (I used frozen).
If using an airfryer, cook for 4-5 minutes. If using the oven, cook for 12-15 minutes, or until the custard center sets (it should jiggle as a whole but not ripple when moved) and starts to caramelize slightly.
Enjoy warm with a drizzle of maple syrup!