Julie Vu knew where to find the right baguette for her bánh mì sandwiches at City Càphê, the Vietnamese luncheonette she was planning to open this month in the City of London. She just wasn’t sure she could find it within 100 miles of Ironmonger Lane.

The baguette she grew acquainted with on forays to Vietnamese sandwich shops in the Belleville quarter of Paris was crackly but not hard, its thin crust giving way to an airy interior without the chewy, open-holed texture of traditional French baguettes. In London she sampled dozens of prototypes but despaired of sourcing anything exceptable until, voilà, she thinks she has it.

I wasn’t invited to Friday’s staff sampling of bánh mì in advance of the official opening on Monday (7 September). I just happened to be in the area, scouting burgermonday possibilities, when I spotted the City Càphê from afar. It’s amazing how my distance vision improves when the subject relates to coffee (càphê is Vietnamese for café). I entered the adorable shop and saw that Julie (left) and her friend Fiona Duong (center) were offering samples of their bánh mì.

The baguette, as viewed in this detail of sandwich cross section, looked bready to the eye, but its airiness was immediately apparent upon first bite. The interior compressed into the fillings as the flaky shell shattered in my mouth. Yum. Yes, I think she has it.

The three varieties of bánh mì I tried were already good, if a little plain, and likely to get better. With her baguette in hand Julie is prepared to think more about fillings and proportions as well as delve into more philosophical questions, such as: to mayo or not to mayo? Authentic or not I am fine with a brush of mayo on the baguette, as long as it’s just a coating and not the main ingredient. For mayonnaise sandwiches in which chicken, beef, pork, tuna and egg are merely accessories we already have Pret.

City Càphê – 17 Ironmonger Lane, London EC2V 8EY