Pre-heat the oven to 180’C
To make the mash, simply cook the potato in boiling water for 20 minutes (adding the cauli and broccoli for the last 7 minutes), or until soft enough to mash.
Once cooked, strain and then return to the heat and give the pan a good shake to get rid of any excess moisture. Mash the potato together with the mustard and the truffle oil and set aside until you’re ready to top.
To make your filling, heat a splash of oil in a large saucepan and fry the onion until soft.
Add the leeks, broccoli and cauliflower and cook for a further 5-7 minutes, stirring regularly to prevent them sticking to the pan.
Add the cherry tomatoes, beans, tomato puree and herbs to the pan, bring to the boil and then simmer for 15 minutes.
Turn off the heat and stir in the tuna, feta and mayo and season to taste.
Pour the filling into a small-medium sized oven dish and then pipe the potato on top (you can just spread it but I find if you pipe it then it goes much further).
Top with the parmesan cheese and then bake in the oven for half an hour.
Once cooked serve up with some seasonal veg and enjoy.