You will need duck confit (recipe is here) to make this, but know that once confit is made it keeps in the fridge for a month or so, and freezes well. If you made the achiote verde it will keep a long time in the fridge. The salsa will not, however. You need to eat that within a day or so.
Have everything set before you begin, as this will come together quickly. Either buy or make the achiote verde, and make the tomatillo salsa verde ahead.
Boil the diced cactus paddles in salted water for 12 minutes. After they've boiled 5 minutes, add a pinch of baking soda; this helps the cactus keep its color and reduces slime. Shock the cactus in ice water to cool.
To finish the salsa, mix together the salsa verde, the corn and the cooked, cooled cactus paddles. Set aside.
Lay the chopped confit in one layer in a large frying pan with as much of the confit fat as you'd like; I use a good 1/4 cup. Sear over high heat for 90 seconds without touching so you get some crispy bits. Stir, and add the achiote verde and the chicken broth. Boil this away until the pan is almost dry again. When you hear the cooking switch from boiling to sizzling, turn off the heat.
Serve with warm tortillas, the salsa and any other accompaniments you'd like.
I used 6 specklebelly goose legs for what you see in the bowl. Four or 5 domesticated duck legs would be equivalent, as would about 12 to 18 mallard legs.