PARIS — I glanced once more at the message on my screen as the Eurostar, the high-speed train from London, docked at Gare du Nord. “I have managed to get all days off while you are here,” my doppelganger had written. “Did I mention how excited I am! Feel like a kid about to meet her pen pal for the first time. . . . Even have the butterflies!”

I thought I was unique until Hillary Nangle, a Canadian expat, found me on Facebook. “I’ve been looking for another Hillary Nangle for a while,” she had messaged, noting that she spelled Hillary with two Ls, whereas I do so with one. “If I must have a double, France is a nice place to have one!” I had replied. Not only did she live in Paris, but also she was a chef at Lenôtre, the renowned culinary company founded by chef Gaston Lenôtre. Ooh-la-la! It was as if I had won the Facebook lottery.

Our galaxies collided in early March. I was researching an upcoming trip through England, Scotland, and Wales on the Rail Europe website when I had one of those V8 moments: I could add on a few days and take the Eurostar from London’s St. Pancras station to Gare du Nord. “Ready to show me Paris, cybersis?” I messaged. “Love LOVE LOVE the idea!” she replied, setting our rendezvous in motion.

And now, here I was, anxiously anticipating meeting my Facebook double. When I had asked how we would find each other in the busy station, she had texted: “Did I mention I’m 6 feet tall? . . . And like to wear heels? I’ll be the one sticking out of the crowd. . . . Literally!” As promised, she was front and center on the train platform, simultaneously waving and snapping pics with her iPhone. Within minutes any apprehensions I had about spending three days touring Paris with a semi-stranger vanished. From the minute I stepped off the train at 10:47 on that Saturday morning until I departed at 4:13 on Monday afternoon, we didn’t stop laughing or, it seemed, eating.

I had found a reasonably priced hotel right around the corner from Hillary’s apartment in the 7th arrondissement. My en-suite room at the Hôtel du Palais Bourbon (49 rue de Bourgogne, 011-33-01-44-11-30-70, www.bourbon-paris-hotel.com, from $125) was barely wide enough for a single bed, but the rate included Wi-Fi and a continental breakfast.

Over coffee at a nearby cafe with views of the gold dome of Les Invalides, Hillary shared her plans for my Paris binge. We strolled to the Metro station, and she gestured to the Eiffel Tower: “That’s my girlfriend. She’s always there, and at night she winks at me.”

When touring Paris with a chef, one expects to eat well. And we did, beginning with lunch at Comme A Savonnieres (18 rue Guisarde, 011-33-01-43-29-52-18, $18-$35) in St. Germaine des Pres. This was no tourist spot. We were the only ones speaking English; the blackboard menu provided no translations; and the decor — stone walls, red banquettes, exposed beams — was textbook bistro. Hillary had brought me to a place Paris chefs whisper about to each other. Chef-owner Valentin Roulière, the son of a Loire Valley butcher, prepares authentic French dishes. We ordered wine, savored the amuse-bouche, then indulged in a three-course meal that ended with a to-die-for thin-crust pear tart topped with caramel and salted butter ice cream.

As we waddled out and through the neighborhood, my new friend introduced me to scarves. “Every French woman is born knowing how to wear them,” she said, toying with the one draped artfully around her neck. Glancing around, I realized I was one of the few women without one. It probably marked me as a tourist, I thought. So did my rudimentary French. I lamented about my grammar skills. “Oh, French is easy,” Hillary quipped. “I figure that because I’m female, everything is female, unless I don’t like it, then it’s masculine.”

We passed a storefront with a line extending out the door and down the sidewalk. “Pierre Hermé makes some of the best macarons in Paris,” she said. Too full to even consider sampling one, we pressed on to Eglise Saint Suplice (2 rue Palatine, 011-33-1-44-07-29-57, free), a flamboyant Baroque cathedral where the Marquis de Sade was christened and Victor Hugo was wed. It earned contemporary fame in “The Da Vinci Code.” Interior eye candy includes frescoes by Eugene Delacroix, a 6,588-pipe organ, and a meridian line designed to predict the date of Easter each year.

Sunday morning we hit the ground running, determined to cram as much of Paris as possible into my sole 24-hour day. We began with the Rodin Museum (79 rue de Varenne, 011-33-01-44-18-61-10, www.musee-rodin.fr/en, $8 or $13 family), located less than a block from my hotel. Since it was the first Sunday of the month, admission to the Rodin, like most museums in the city, was free. It was crowded, but not impossibly so.

Inside the early-20th-century chateau-style mansion and throughout its gardens are nearly 300 sculptures and paintings by Rodin. We ogled “The Kiss,” peered into “The Gates of Hell,” marveled at the “Marble Gallery,” and pondered “The Thinker.” I tasted my first authentic macarons at the museum’s cafe.

Next stop, The Cluny, or National Museum of the Middle Ages (6 place Paul Painlevé, 011-33-0-1-53-73-78-16, www.musee-moyenage.fr/ang/, $11), a treasure of medieval artifacts and artwork housed in a 15-century Gothic mansion built atop the ruins of Roman baths. We raced through exhibits, spending the most time at Hillary’s favorite, “The Lady and the Unicorn,” a six-panel tapestry woven in Flanders between 1485 and 1500.

We whiled away the waning afternoon hours strolling in the Latin Quarter. Students, lovers, and families lounged and picnicked on the banks of the Seine. We jockeyed for position to snap pics of Notre Dame; stared back at Parisians of all stripes, who watched us from their seats at outdoor cafe tables, sipping café au laits; and wandered narrow streets lined with cafes and shops. And then we ate again, ducking into L’auberge du Moulin (22 rue de la Huchette, 011-33-0-1-43-54-18-13, $18-$30) for escargot, a ham-and-cheese crepe, and raclette with a charcuterie plate. More walking, more wandering, more wine, and then Hillary realized that if we hurried, we could make it to the Eiffel Tower for its hourly flash dance, an entrancing sight.

We spent our final morning strolling the Champs Élysées, stopping into the Lenôtre center, where Hillary occasionally teaches. Our timing was perfect, as I was able to meet one of her mentors, Philippe Gobet, a master chef of France and director of Ecole Lenôtre.

We ended our visit with traditional Breton-style crepes at the Crêperie du Manoir Breton (18 rue Odessa, 011-33-01-43-35-40-73, $15-$25). Made with buckwheat flour, Breton-style crepes have a dense texture and an earthy, nutty flavor. Instead of being wrapped around a filling, they are served flat, with the edges folded over the ingredients and often topped with a fried egg. Hard cider is the usual accompaniment. After savoring one filled with ham, Gruyère, and egg, we gilded our cyber-sisterdom by splitting a chocolate one.

“I think we need to search Facebook for Hilaria Nangli, a winemaker with a vineyard in Tuscany,” Hillary mused. “Ciao!” I replied enthusiastically, and headed for my train.