The schoolgirl, from East Dunbartonshire, stayed cool in the kitchen as she competed against the top young cooks from across Scotland.
She was taking part in a special cook-off for the Young Chefs of the Future contest at Glasgow Science Centre.
And the judges described her dessert as "10 out of 10 – a dish any a la carte menu would be proud to have."
The competition, which was open to children in primaries four, five, six and seven, attracted more than 100 entries from all over Scotland.
Run by Glasgow Science Centre, it asked would-be chefs to prepare a menu for their favourite scientist.
The final six had to showcase their main courses and desserts at a special cook-off in City of Glasgow College, working alongside some of Scotland's best professional chefs.
Elissa's mentor, Simon Whitley – executive chef at the Hilton in Glasgow – said all three competitors were fantastic.
"The standard in this year's competition is extremely high and it's been great working alongside these young chefs," he said.
"Competitions like this really encourage young people to enjoy cooking and it's great to see such imagination and flair."
Elissa's inventive menu – which she called A Fleming Discovery – was designed for Sir Alexander Fleming, who discovered penicillin.
The 11-year-old said: "My main course was mushrooms stuffed with chorizo, walnuts and blue cheese on a green asparagus salad called Mould and Fungi Feast, because Fleming discovered a mould which stopped bacteria growing and it went on to save billions of lives.
"My dessert – a chocolate fondant with raspberry cream – is called Oozing Boil with Antiseptic Cream' because Alexander Fleming also did a lot of medical work investigating boils."
Judges, who included Joe Queen of Braehead Foods and Glasgow Science Centre chef Kenny Meechan, said Elissa's main course was "superb" and had shown a lot of imagination.
Joe added: "The dessert is absolutely beautiful – a restaurant could charge £8 or £9 easily for that dish – it's fantastic."
Elissa, who won a special Food Miles award for her careful consideration of where the chorizo in her main dish had travelled from, said: "I'm really pleased just to be here because it's a wonderful experience.
"I love cooking but it is just a hobby as I plan to be a cancer surgeon when I leave school."
Elissa, who has two sisters, Jenny, 12 and seven-year-old Hannah, said she got her love of cooking from her parents.
"My mum follows recipes and my dad makes it up as he goes along, so I do a bit of both," she says.
Elissa missed out on the top prize to last year's winner Bethia Swan, 10, from Pittenweem, who defended her title with a colourful pan-fried salmon and spiced lentil main course, and apple and plum crumble with blueberry mascarpone cream dessert.
Third place in the primary six and seven category went to 11-year-old Lynsey Brown from St Andrews.
The winner of the primary four and five category was Pani McDermott, 8, from St Andrews, while Seumas Clark, 9, from Islay and Nicholas Redford, 10, from Troon, took second and third places respectively.
The winners get to attend Glasgow Science Centre's, A Taste of Science Dinner next month, hosted by celebrity chef and TV presenter James Martin. They also receive an annual family pass to Glasgow Science Centre, a medal and their own professional chef's apron.
James Martin said: "I am looking forward to coming to Glasgow Science Centre to host A Taste of Science and meet the winners of the Young Chefs of the Year winners.
"Scotland has a great range of cookery talent with Michelin star chefs such as Martin Wishart, Gordon Ramsay, Andrew Fairlie and Tom Kitchin.
"The contest is a great opportunity to inspire the next generation to follow in their footsteps."
Glasgow Science Centre's commercial events co-ordinator Kerry Bottomley said: "The Young Chef of the Future competition embraces our fundamental aim – to encourage interest in science. It helps children to understand that cooking is all about science – an experiment of flavours, tastes, techniques, reactions and results.
"With invaluable support from Skills Development Scotland, Young's Seafood and Springboard Scotland, the competition has shown just how enthusiastic and sophisticated young children are about what they eat and has showcased the talents of six talented young chefs from all over Scotland."