Creamy tom yum rigatoni with shrimp

This comes from a blog called Store-Bought Is Fine, which I take personally, and I will admit the jar of tom yum paste has earned its place. It does in a spoonful what would otherwise mean a pile of lemongrass, galangal and lime leaves. Read the jar before you buy it. Tom yum soup is usually made with mushrooms and some pastes carry mushroom extract or powder. Plenty of good ones do not.

The original wore a chimichurri on top. With cilantro running the show, lime instead of oregano and a serrano in it, it is a green sauce, and we can all be grown-ups about that. It is chopped by hand here, because a blender will not catch this little.

It is a two-season dish. In summer the corn is charred in the pan. In the fall it is butternut squash or kabocha, roasted hot until the edges go dark, and the sweetness does the same job against all that sour and heat.

1. Put a big pot of well-salted water on to boil. If you are using squash, heat the oven to 425°F, toss the cubes on a sheet pan with 1 tbsp of the neutral oil and a good pinch of salt, and roast 20 to 25 minutes, until tender with dark edges. Set aside.
2. Make the green sauce. Zest the lime half and set half of that zest aside for the pasta. Very finely chop the cilantro, parsley, half the shallot, 1 garlic clove and the serrano together on a board, and scrape it all into a small bowl. Stir in the other half of the zest, the lime juice, vinegar, cumin, a pinch of salt and the olive oil.
3. If you are using corn, heat 1 tbsp of the neutral oil and ½ tbsp of the butter in a large skillet over medium-high. Add the corn in one layer with a pinch of salt and leave it alone 4 minutes, then stir and cook 2 to 3 minutes more, until it is charred in spots. Tip it into a bowl. If you cut it off the cob, run the back of a knife down the bare cobs over a cup and keep that milky juice for the sauce.
4. Pat the shrimp dry and season with salt. Heat the rest of the neutral oil in the large skillet (the one the corn came out of, if you used corn) over medium-high and sear the shrimp 1 minute a side, until just pink. They finish in the sauce. Add them to the corn (or the squash).
5. Drop the rigatoni into the pot and cook it a minute or two short of al dente. Scoop out 1 cup of the pasta water before you drain it.
6. Meanwhile, make the sauce. Turn the skillet down to medium and melt the remaining butter. Finely chop the rest of the shallot and slice the second garlic clove, and cook them 1 minute. Add the tom yum paste and fry it, stirring, 30 seconds, so it sizzles in the butter before anything wet arrives.
7. Pour in the coconut milk, cream and any corn juice, and simmer 4 to 6 minutes, until it thickens enough to coat a spoon. Stir in the fish sauce and the reserved lime zest, and season with pepper.
8. Drain the pasta and tip it into the sauce with the corn or squash and the shrimp. Toss over medium-low for a minute or two, loosening with pasta water a splash at a time until the sauce is glossy and flows. There is only a little cream in it, so it will want more water than you expect. Add pepper flakes if you like it hotter, then taste for salt.
9. Divide between bowls and spoon the green sauce over the top.