Start by cutting the milk buns into cubes and setting them aside. Chop the strawberries and rhubarb into small, even pieces so they cook uniformly. Grease your baking dish lightly with butter to prevent sticking and enhance flavor.
In a mixing bowl, whisk together eggs, milk, sugar, vanilla extract, and cinnamon until smooth. Make sure the sugar dissolves well to avoid graininess. The mixture should be creamy and slightly thick.
Place the cubed buns into the greased dish and scatter the fruit evenly on top. Pour the custard mixture over everything, ensuring all bread pieces are soaked. Let it sit for 5–10 minutes so the buns absorb the liquid fully.
Preheat your oven to 180°C (350°F) and bake the pudding for about 35–40 minutes. The top should turn golden, and the center should be set but still slightly soft. Avoid overbaking to keep it moist.
Remove from the oven and let it cool for a few minutes before serving. This helps the pudding firm up slightly and enhances the flavors. Serve warm for the best taste and texture.