Choose Between Two Options

• $12 for three Groupons, each good for $7 toward coffee and pastries $21 value)
• $15 for two dozen donuts ($24 value)

Filled Donuts: Flavor Injection

Spend a little more time in contemplation of your hot, fluffy pastry with Groupon’s look at how donuts get filled.

Bite into the soft midsection of a donut packed with jelly, custard, cream, or any other decadent cargo and it may seem a little magical: how does the filling get inside, and stay there without leaking out? In most cases, the answer is quite simple: after the donut comes out of the oven, the baker grabs a pastry bag equipped with a long, sharply angled metal piping tip, pokes it through the side of the donut, and squeezes in a petite dollop of filling. (It’s best to do this while it’s still hot, so that the dough will easily stretch without tearing and the sticky filling will set slightly to seal the hole.) Larger bakeries get a little mechanical help in this process with machines programmed to dispense a certain amount of filling at the push of a button, but the principle remains the same. Scan the side—or, in the case of an éclair or a long john, the end—of a filled donut, and you’ll probably see a small mark where the tube has been poked in.

If you don’t, there is a second option: the baker makes three rounds of dough, eats one, spoons filling onto another, and secures the other on top before frying. This works best with fruit fillings, which can stand up to heat; although it does introduce the risk of donuts coming apart in the fryer, the method more easily accommodates larger blobs of filling.

Once you know how to fill donuts at home, you can replicate a classic German practical joke. At New Years’ Eve parties, Germans are known for secretly filling a couple of donuts with mustard to predict which friendships they’ll lose in the new year.