The 28-year-old party planner - who is the Duchess of Cambridge's younger sister - has enjoyed a string of dates with 37-year-old James Matthews in recent weeks and friends say their relationship is going "from strength to strength".
An onlooker at London's Hakkasan restaurant, who saw the couple on a recent date there, said: "Pippa and James sat in a secluded booth in the upstairs area, where it was quieter, sharing a bottle of white wine.
"They were deep in conversation and only had eyes for each other.
"Pippa was all smiles and kept giggling. They stayed for nearly three hours and didn't seem to want the meal to end."
Middleton - who has been largely single since splitting from Alex Loudon last November after three years together - had been focusing her attentions on her new book Celebrate: A Year of British Festivities for Families and Friends but now the party guide has been released, she is ready to love again.
A friend told the Sunday Mirror newspaper : "Pippa is quite taken with James. She wants to take things slowly at first but she is ready for a full-time man in her life again."
James Matthews is the older brother of Spencer Matthews, who stars on UK reality TV show Made in Chelsea.