According to the Made In Chelsea star, she cooks a traditional festive meal, but of course without the meat and dairy.
She was speaking to Wren Kitchens after renovating her kitchen.
"The maths that goes with cooking for a big group at Christmas is quite stressful," Watson said, in the interview which was shared with Plant Based News.
"I manage to get to a point where there is one potato left, leaving everyone full but everything is gone. My favorite part of cooking Christmas dinner is the roast potatoes, they are so important."
Watson said she parboils potatoes before roasting them 'so they are fluffy' before throwing them in a sieve, and covering them with rosemary and olive oil.
"I pair that up with a Tofurkey – a tofu Turkey. Which makes the mains of my Christmas," she added.
"I also have a great mince pie recipe in my new book which is really simple to make. People tend to love a mince pie, and these taste exactly the same as a regular one and gives me that festive feeling. I love all kinds of Christmas recipes especially a Christmas roast."