Heat 2 tablespoons oil in a large skillet over medium heat. Add onion and sprinkle with ¼ teaspoon salt. Once the onion starts sizzling, reduce heat to medium-low. Cook, stirring occasionally, until the onion is golden brown and jammy, about 40 minutes.

Meanwhile, mash garlic with the remaining ⅛ teaspoon salt on a cutting board with the back of a fork or side of a chef's knife.

Add the garlic paste to the pan and increase heat to medium. Cook, stirring, until fragrant, about 30 seconds. Add the remaining 1 tablespoon oil and aji amarillo paste; stir to combine. Cook, stirring, until the oil separates, about 30 seconds. Add vermouth and cook, stirring, until it evaporates and the oil separates again, about 30 seconds. Add quinoa and stir to combine.

Add 2 ½ cups broth to cover the quinoa. Let simmer, stirring occasionally, until the quinoa has absorbed most of the liquid and you begin to see tiny holes in the quinoa, about 20 minutes. (If the quinoa appears to be sticking to the pan, reduce the heat slightly.)

Stir in oregano. By this point, most of the quinoa should have burst and become translucent. If you still see some white spots, gradually add ½ cup broth, little by little, stirring constantly, until the quinoa is fully cooked.

When the quinoa has the consistency of stiff mashed potatoes, reduce heat to low and add evaporated milk and Parmesan. Cook, stirring occasionally, until it has a risotto-like consistency, about 5 minutes. Garnish with parsley and peas, if desired.