LOS ANGELES — Jonathan Grahm, the owner of Compartes Chocolatier in Brentwood, Calif., is just back from a whirlwind pre-Valentine’s Day tour of Japan, where 100 Compartes pop-up shops opened for the holiday in Tokyo, Osaka, Yokohama, Hiroshima, Nagoya and Kobe. Grahm’s face has been plastered on billboards, little old ladies in kimonos vied for his autograph, designers wanted his chocolates to coordinate with their products (underwear, for example) and fans showered him with gifts (such as a Mickey Mouse action figure).

He is, as they say, big in Japan.

After winning a chocolate competition in Tokyo that pitted him against dozens of European contenders and brought him outsized media attention, Grahm has eight permanent Tokyo stores and is about to open another in Shanghai. But the 28-year-old chocolatier aims to be the face of American chocolate in his hometown.

“I’ve been sort of under the radar” in L.A., says Grahm, who is puckish and inclined to wear button-down shirts with colorful bow ties. He has been Compartes’ chocolate maker since he was 21. Four years ago, he bought the business from his family when they were about to give up on it and has since rebranded and expanded.

The recently renovated shop looks “like the Prada of chocolates,” noted one customer.

Grahm is now selling his chocolates wholesale to select retailers such as wine store DomaineLA and Farmshop’s gourmet grocery, with more to follow. And he’s about to double the size and production capacity of his chocolate workshop, after increasing sales volume by four times in the last five years (not including sales in Japan).

His proudest recent accomplishment? An elaborate, fantastical line of 24 new chocolate bars that were two years in the making, with no-detail-too-small packaging that he designed, covered in palm trees, chevron patterns, houndstooth, skulls, volcanoes, snakes, African and ancient Roman art, hieroglyphics, his own photos or other intricate imagery. “I like to think of myself as a culinary explorer, and my medium, of course, is chocolate.”

Just as the packaging was about to go to print, he decided to write haiku-type descriptions for each chocolate bar. A bar called Coney Island is milk chocolate with crushed pieces of waffle cone, whose box is covered in unicorns and an ombre rainbow of neon colors: “Cone-headed unicorns merrily go round as waffle cones are filled with deliciousness in the days of the endless summer.”

“I had 30 minutes — total — to write them, and they just poured out of me,” Grahm says, and when he finished, “I cried, literally bawled, for about five minutes and let it all out. I can’t believe I finished this project all on my own.”

Grahm went to Beverly Hills High, then UCLA before giving up on his political science major to become a full-time chocolate maker at Compartes. Entrepreneurship runs in the family: His parents had an import-export business; his uncle, acclaimed winemaker Randall Grahm, started Bonny Doon Vineyards; and his grandmother, Ruth Grahm, famously helped sell Bonny Doon by knocking on every restaurant door in L.A. with a grocery bag of bottles.

“Going around to the best restaurants in L.A. with Ruthie and her wine basket helped shape my career and path,” Grahm says. But he also attributes his palate to experiences with his late mom, a world traveler who spoke eight languages and took Grahm to Venezuela in the summers to visit her sister. “Getting to go to summer camp and literally sleep in the rain forest and taste tropical fruits definitely inspired my flavors, and I, of course, love Venezuelan chocolate.”

A self-taught chocolatier, he skews toward the exotic and is known for ganaches that combine fruit and spice, which he calls “three-dimensional”: blackberry sage, rose pistachio, pineapple habanero, mango saffron, peach rosemary. For Valentine’s Day, special flavors include raspberry rose, lavender Meyer lemon, strawberry Champagne, raspberry pink pepper and huckleberry rhubarb. But he also stays true to the nostalgic, partly in honor of Compartes’ roots as a 1950s chocolate shop (he recently changed the name slightly by moving the apostrophe in Comparte’s over to become an accent on the “e”). That means chocolate-dipped strawberries.