Combine sugar and water in a saucepan over medium-low heat. Bring to a simmer, stirring constantly until sugar dissolves and mixture becomes a light brown syrup. Holding the handle of your pan, gently tilt the pan off the heat to distribute syrup evenly. Immediately pour into bundt pan or pie dish. Coat the base of the pan evenly by tilting the pan/dish and swirling the syrup around the base. Set aside and allow to cool.

In a medium-sized saucepan, combine the milk, sugar and orange peel. Stir to dissolve the sugar in through the milk and bring to a slow simmer on medium-low heat. Allow milk to simmer for 20 minutes. Stir through the vanilla, remove milk from heat and allow to cool for an hour until completely cool.

Adjust oven rack to middle of the oven and preheat oven to 176C | 350F.

In a bowl, beat the eggs with a hand-held mixer at medium speed for about 3 minutes until light and fluffy.

Once the milk has completely cooled, remove orange peel and pour it through a fine strainer. Gradually beat the cooled strained milk in to the eggs. Beat on low speed until air bubbles are out. Pour flan mixture into pan/dish and place into a a larger oven-proof pan.

Pour hot water into the larger pan to within 1-inch of top of the flan pan/dish. Place pan on the middle rack of the oven. Bake 50 - 55 minutes or until set to the touch.

Remove from oven and leave in the water bath until cooled. Remove pan/dish from water and refrigerate overnight.

To unmold and serve, place serving plate (topside down) on top of flan. Flip the custard pan onto the plate and carefully lift off cake tin.

Break up toffee into pieces with a knife, and serve flan with toffee and (optional) orange slices.