Prep filling. In a small bowl, combine peanut butter and maple syrup and mix well until combined. Peel banana, then slice in half down the middle, then thinly slice lengthways.
Prep toasts. In a shallow medium bowl combine eggs, cinnamon and milk, whisk well with a fork. Spread peanut butter filling evenly on all four slices of bread. Add sliced banana to two of the slices. Close remaining two slices on top of banana, peanut butter facing inwards, to create two sandwiches.
Cook toasts. Place both sandwiches into the egg mixture. Leave to soak for about 3 minutes, flip over and leave for a further three minutes until bread is soaked through. Heat oil in a medium frying pan on medium heat. Transfer soaked toasts to pan and cook for about 3 minutes each side, until golden and filling is warmed through (lower heat if needed).
Serve, stuffed French toast dolloped with yoghurt.