A dish like spaghetti puttanesca—spaghetti in a sauce with tons of olives, capers, and anchovies—is supposed to be a quick and easy meal, but if you don't know how to efficiently chop olives and capers, it can turn into a tediously painstaking affair.
Chopping olives and capers (whether salt-packed or brined) seems like a "duh" kind of skill at first glance, but go into it blind and you'll find yourself frustrated. Whole olives (I typically recommend buying whole olives over pitted, as their flesh has a nicer texture) have a hard, clingy pit to contend with. And as for capers, well, once you've got them out on the counter and you try to take a knife to them, you'll find that keeping them in place while you chop is like trying to contain a deck full of tribbles.
These are the easiest ways I know to deal with them.
How to Pit and Chop Olives
I used to work at a restaurant where slicing olives meant meticulously slitting them open with a paring knife like you would an avocado, picking out the pit with the tips of your fingernails (a task that's easier said than done!), then carefully slicing each half into little half moon–shaped filets. Sure, it made the dish look great, but oftentimes, in fine-dining, conspicuous consumption–type restaurants, I felt like many of the tasks we performed in the kitchen were solely for the purpose of justifying a bigger price tag.
At home, I use a much more straightforward approach that takes about a tenth of the time, and looks a little messier, but tastes pretty much exactly the same. I call it the smash-and-pick.
Step 1: Smash the Olive
Place an olive on your cutting board, then lay the flat side of your knife on top of it. Smash down on the knife very firmly (like you're crushing a garlic clove, or perhaps buzzing in during the face-off in Family Feud).
You may want to wear an apron for this, especially if you're smashing black olives, since their juice can spray and stain.
If you do it right, the olive should split open, revealing the pit.
Step 2: Pop the Pit
Pull the two split halves of the olive apart and poke out the pit with your finger (if it didn't already just fall out on its own).
Step 3: Chop
Discard the pit and chop the flesh of the olive with a sharp chef's knife, slicing for filets or rock-chopping with your free hand on the blade end of the knife for a fine mince.
The most efficient way to chop lots of olives is to work like an assembly line, doing one step at a time: First, smash all the olives; then put down your knife and pop all the pits; then, finally, chop all the olives. It's much faster than picking up and putting down your knife for each individual olive.
NB: For some very young, firm olives, this method will not work. For those olives, unfortunately, your best method is the old restaurant technique: Split the olive open, then use your fingernails to carefully prise off the flesh.
How to Chop Capers
The secret to chopping capers is to dry them and alter their shape so they stay put. Here's how I do it. If you're using salt-packed capers, proceed with Step 1 after thoroughly rinsing and draining them.
Step 1: Fold Up a Paper Towel
Fold a paper towel into quarters so that you end up with a quadruple layer of paper towels. (If you're cutting a lot of capers, you'll need to work in batches or use a double paper towel for more surface area.)
Step 2: Press Capers Hard
Place the capers on one half of the folded paper towel, fold the other half over the top, then press down on the capers very hard. The goal here is not only to get excess moisture off of them, but to actually flatten them a little bit. This will prevent them from rolling around.
Step 3: Transfer to Cutting Board
Transfer the flattened capers to your cutting board.
Step 4: Chop
Now chop the capers using a sharp chef's knife, slicing back and forth for a rough chop, or placing your free hand on the tip of the knife blade and rocking rapidly for a fine mince.
Chopped capers can be stored in a sealed container in the refrigerator for several weeks.