A single large Gold potato is usually around a pound. You can either cube a single potato for this recipe, or you can use two potatoes to get a pound worth of fry-style slivers.
Add the chopped potato to some boiling water and cook for a few minutes. I give them just a quick swim to get a headstart on cooking, about 3-4 minutes. Drain the potatoes and set them aside until you need them.
Peel and roughly chop the 1/2 onion and 4 garlic cloves.
Heat a glug of oil in a medium-sized saucepan over medium heat. Saute the onion and garlic for a few minutes until the onion has softened.
Add the spices to the onion-garlic mixture: 1/4 teaspoon cumin seeds, 1/2 teaspoon Mexican oregano, 8-10 black peppercorns. I usually give the spices a quick crush in the molcajete but this is optional. And feel free to use powdered spices if you don't have seeds or peppercorns on hand. Cook briefly.
Rinse and de-stem the jalapenos, chopping them up into coin-sized slices. I used 3 jalapenos but you can always use less for a milder batch. Add the sliced jalapenos and drained potatoes to the pan. Cook briefly and then add the remaining ingredients: 1 tablespoon salt, 1.5 cups white vinegar, and 1 cup water.
Give it a good stir and bring this mixture up to a boil. Once it's boiling you can transfer the mixture to a quart-sized Mason jar (or two pint-sized jars). I usually use tongs to add the veggies to the jar and then pour the vinegar mixture all the way to the brim. You can give the papas a taste test now for a preview, but they won't have full flavor until they rest overnight in the brine.
I usually let the jar cool on the counter for a bit, then cap and store it in the fridge where it will keep for weeks at a time.