Over the course of his more than 50-year career, Warren Buffett has made plenty of high-profile moves. But according to a fascinating story in newsletter The Hustle, Buffett's personal favorite investment is one you've most likely never heard of. 

Forget his high-profile stakes in the likes of Apple, Coca-Cola, and Amazon. Buffett's favorite investment is in a small, slow-growing confectionary chain called See's Candies. He once called the unsexy company his "prototype of a dream business." 

What sets boring-seeming See's apart? Understand that and you'll understand exactly what constitutes a great company in the eyes of the world's best investor. 

Substance beats flash  

One thing that The Hustle's deep dive makes clear is See's is definitely not flashy. Started by a retired hotel keeper and her son in 1921 and famed for its obsession with quality, the brand has chugged along for nearly 100 years with modest growth in stores and sales volume of only 2 to 3 percent per year. 

"The boxed-chocolates industry [is] unexciting," Buffett admitted to shareholders in 2007. "Per-capita consumption in the U.S. is extremely low and doesn't grow."

But what See's lacks in growth, it makes up for in customer loyalty, earned through its uncompromising approach to quality. When the brand threatened to discontinue a handful of products in 1987, for instance, outraged fans showered so many curses and complaints on the firm it was forced to reverse course. 

That level of customer obsession has allowed Buffett to steadily raise prices by 10 percent a year. That combined with the company's slow-but-steady growth has added up to a river of revenue for Berkshire Hathaway.

"See's sales crept up to $383 million by 2007 (with $82 million in pretax profits), and an estimated $430 million by 2018. Since 1972, the company has given Berkshire Hathaway well over $2 billion in income. That's a return of more than 8,000 percent, or 160-plus percent per year. Over the same time period, the small operation required only $32 million in capital to run," explains The Hustle. 

"Just as Adam and Eve kick-started an activity that led to six billion humans, See's has given birth to multiple new streams of cash for us," Buffett said of the little company that could. Those profits funded many of Buffett's more high-profile investments. 

A healthy reminder for our growth-obsessed era 

The Hustle's detailed and chart-filled history of the whole See's story is well worth a read in full, but what's the key takeaway here? The value of customer loyalty and the importance of quality in gaining it are a couple of obvious lessons. 

But probably the most important takeaway is that substance beats flash. In an era where companies often chase impressive growth while running up huge losses (hello, Uber and Slack), Buffett's all-time fave investment is a reminder that, at the end of the day, the game is making money after all. Sometimes the best way to do that isn't to grow big fast but to choose a great if boring business and run it really well for the long term.