The prosecution also told the jury that Erin Patterson told her estranged husband she wanted to make a "special meal" for his family before she allegedly fed them death cap mushroom-laced beef Wellingtons, a jury has been told.
The prosecution has begun to outline its case against Patterson, 50, who faces a six-week trial at Latrobe Valley Law Courts in Morwell, 155km southeast of Melbourne.
She has pleaded not guilty to three charges of murder and one of attempted murder over the lunch at her Leongatha home in July 2023.
Her former in-laws, Don and Gail Patterson, and Gail's sister, Heather Wilkinson, all died in the hospital after consuming the lunch.
Ian Wilkinson, a local church pastor who was married to Heather, was the only lunch guest who survived, and Patterson is charged with his attempted murder.
Crown prosecutor Nanette Rogers SC opened her case on Wednesday when she revealed alleged Patterson wanted to hold the lunch to seek advice on telling her children about medical issues.
Patterson invited all the guests to the meal, along with her estranged husband Simon, at a Sunday service at Korumburra Baptist Church, where Ian was the pastor, Dr Rogers told the jury.
The day before, on July 28, Simon sent a text to Patterson declining her lunch invitation because he felt "uncomfortable" but was happy to talk about Patterson's health another time, she said.
Dr Rogers said Patterson, in her reply to Simon, "emphasised the effort she put into the lunch and said she wanted it to be a special meal and she may not be able to have a lunch like this for some time".
It was alleged that Patterson organised for her children to be out of the house for the lunch on July 29.
After her former in-laws and Heather and Ian Wilkinson arrived at her home, Patterson served up individual beef wellingtons consisting of a piece of steak covered with mushrooms and wrapped in pastry, Dr Rogers said.
She served Wellingtons with mashed potato and greens and gave her guests four large grey dinner plates while she ate her meal off a different small tan-coloured plate, the jury was told by Dr Rogers.
"They said grace and started the meal. Ian and Heather ate an entire portion, Gail had half a serve, and Don ate hers and his," Dr Rogers said.
"There was banter amongst them about how much they'd eaten."
After the main meal, the group tucked into a dessert of cake and a fruit platter brought by Gail and Heather, Dr Rogers said.
It is alleged that Patterson then revealed to the group she had cancer and asked their advice about telling her children. They told her it was best to tell them.
With AAP.
