This secret ingredient makes apple pie extra apple-y.  

Love it or hate it, McDonald’s knows how to keep customers coming back for more. We already know why its Coke is so much better than anywhere else--now it’s time to uncover another McDonald’s mystery: What makes the apple pies so. damn. good?

Mickey D’s added its first dessert in 1968 and fans have been smitten ever since. Here’s why:

First, the apples themselves play a role. If you thought you could make a comparable pie with basic Red Delicious apples, think again.

WATCH: How to Make Pie Dough

The recipe calls for six different apple varieties including Jonagold, Fuji, Golden Delicious, Gala, Rome, and Ida Red.

That’s a lotta apples. But the real reason the $1 dessert is in a class of its own has to do with how it stays together.

Many fruit pies rely on processed thickening agents to set their fillings. McDonald’s, Stella Parks tells Thrillist, uses a dehydrated apple powder that pulls double duty: It soaks up the liquid that’s released during the baking process, and it also adds a flavor punch for an extra apple-y apple taste.

There ya have it. Next time you’re guzzling McDonald’s Coke between bites of McDonald’s pie, at least you’ll know why you can’t stop.