Ingredients :

• Feta in a block, not crumbled — This is the only point on which you must not compromise. Crumbled feta contains anti-caking agents that prevent it from melting correctly — you end up with floating white lumps. A block in brine, however, melts into a creamy and homogeneous mass. Look for Greek PDO feta if you can find it.
• Cherry tomatoes — Get the smallest ones you can find. They burst better under pressure, and their skin-to-flesh ratio releases more sweet juice into the sauce. If you only have regular tomatoes, cut them into quarters — the result will be slightly less punchy but perfectly fine.
• Penne rigate — The ridges aren’t just for looks: they catch the creamy sauce in every bite. You can use fusilli with the same result. Avoid thin pasta like spaghetti or vermicelli, which cook too quickly under pressure and end up as mush.
• Low-sodium chicken broth — This provides the umami base that balances the saltiness of the feta and the acidity of the tomatoes. An insipid broth gives a flat result. If you want to keep it vegetarian, vegetable broth works very well — but taste before seasoning, as some are already very salty.