Throw all the dry stuff in a bowl and whisk it. That means flour, baking soda/powder and salt, you know the drill.
Next, put the butter, sugar and vanilla in your stand mixer bowl. Zest the lime and add that in too (the zest, not the lime…obviously). Mix it at medium high until it’s nice and fluffy, and don’t hold back, you want this stuff to be smooth.
Mix in an egg until it’s fully incorporated, then do the same for the other one.
Chop up your espresso beans, and give them a rough chop, so you have nice-sized pieces and not chocolate dust.
Add the espresso beans into the batter, and mix on low. Then, add the flour mixture and do the same.
Once you have a fully-mixed dough on your hands, get a big cutting board or other similar flat thing and spread a little flour on it. Do the same for your hands. Turn out the dough onto said flat thing and divide it in half, then roll them both into inch and a half wide logs.
Pat down the top of each log gently, then let them chill out in the fridge for an hour.
Take that last egg and whisk it, then brush the tops of the soon-to-be-biscottis with the egg. Follow that up with a little decorative sugar on top and throw them in the oven for 25-30 minutes. Go towards the low end if you want your biscotti to be a little chewier, or towards the 30 minute mark if you want crumbs all over your floor. Entirely up to you.
After they’ve had a chance to bake, take the biscotti out and make sure it’s got that nice, golden brownness to it. If it doesn’t, throw it back in for a few more minutes. If it does, let it cool for five minutes, then take a serrated knife and cut the logs into diagonal slices.
Turn the slices on one side and put them back in for eight minutes, then flip and do the other sides for another eight, put them on a cooling rack, and you’re done.