Peel the potatoes and cut them into large cubes. Place the potatoes in a microwave dish with a lid. Add ¼ cup of water and microwave on high heat for about 8 minutes. Check to see if they are soft and if not, then put them back for another 2 minutes.
Strain the potatoes to remove the water. Place the potatoes in a big bowl and mash with a fork or masher. Don't add anything to it because it needs to be dry to soak up the other ingredients.
Using a food processor, whizz up the bread into fine breadcrumbs and add to the bowl.
Also, whizz up the zucchini and carrot until finely chopped. Add to the bowl.
Add the tuna, egg and mayonnaise or chutney to the bowl and mix together until well combined.
Then form into patties.
In a non-stick frypan, place a teaspoon of oil and a teaspoon of butter and have the heat on medium. When the butter bubbles, add the patties to the pan.
Turn the patties over after a few minutes. You are looking for a golden brown colour. If they are burning, either turn over earlier or turn down the heat.
You can then place the patties in an oven at 165°C to cook through.