Wash and dry the fennel and potato.

Cut off the stems of the fennel, reserving them for later. Using a grater or a food processor with the grater disc inserted, grate the fennel. If using a food processor, slice off the bottom of the bulb first. Put the fennel in a bowl and set aside.

Shred or grate the potato. If you have time, soak the potato in cold, lightly salted water. This will remove some of the starch, making for a less gluey hash. Drain well and squeeze dry before cooking. Mix evenly with the fennel.

Add the oil to a heavy nonstick frying pan, saute pan, or cast-iron frying pan. Heat the oil over medium-high heat until it shimmers, tilting the pan to coat the bottom. Add the potato-fennel mixture, stirring well as you add it to coat it with the oil. Sprinkle with a small amount of salt as you cook. Let the mixture cook, without stirring, for 5 minutes.

Cook for 5 minutes, then flip the mixture in sections. Cook another 5 minutes. You might need to turn down the heat a little. You want to create a crust on the potato mixture without burning it.

While the hash is cooking, finely mince the thin stalks of the fennel and the feathery fronds.

After 10 minutes, stir in the quinrizo or soy chorizo, mixing well. Cook another 10 minutes, flipping sections of the hash once or twice until the potatoes are completely cooked. Add additional salt, if needed. Top with the minced fronds just before serving.