Step 1: Base ingredients
Add the onions and chilis to a hot oiled pot, and stir until the onions start to soften. Reserve the garlic to add later so more of its flavor will come through at the end. (Alternatively, add the garlic now if you want it to be extra-subtle.)
Step 2: Chayote squash and long beans
They're a bit drier and sturdier than standard green beans, which makes them a good choice for dishes that cook longer or have a bit of sauce. As an extra bonus, they're faster to prep than an equivalent volume of regular green beans since they've got fewer ends to chop off. This is wonderful for those of us looking for shortcuts.
Chayote squash are native to the Americas, hold their shape well when cooked, and accommodate heavy spicing. The cooked texture is not unlike a raw cucumber, making for interesting variety in stews.
Step 3: How to process chayote squash
Quarter it, slice out the seed, peel the skin off, then cut it into bite-size chunks. While both the skin and seed are edible, they're best removed for this use. The color and texture of the uncooked peeled chunks are similar to that of an underripe honeydew melon.
Step 4: Cook
When the pot has come back to temperature add the turkey sausage. Break it up into small bits, and stir periodically to cook through. When the meat is cooked, add a handful of chopped fresh tomatoes. They'll drop some more juice, which should mingle nicely with the chayote juice.
Add some additional seasonings. I used a bit of chili powder, balsamic vinegar, and Worchestershire sauce. Other good options: fish sauce, sriracha chili sauce, anchovy paste, soy sauce, lemon/'lime juice.) You want to build up layers of spice (the serranos, black pepper, chili powder) and give some depth of flavor (the vinegar, worchestershire sauce, boullion cube).
Taste and modify the seasonings as necessary.