Step 1: Prepare the Yum Yum Sauce (Do this first!)

1. Combine Ingredients: In a medium-sized bowl, combine the mayonnaise, tomato paste (or ketchup), melted butter, rice vinegar, sugar, garlic powder, onion powder, and paprika.
2. Whisk Thoroughly: Whisk all the ingredients together vigorously until completely smooth and well combined. Ensure there are no lumps of tomato paste or spices remaining.
3. Adjust Consistency: Check the consistency. If the sauce is too thick to drizzle easily, whisk in 1 tablespoon of water. Continue adding water, 1 teaspoon at a time, whisking after each addition, until you reach your desired creamy, yet pourable, consistency. It should be similar to a ranch dressing or slightly thicker.
4. Taste and Adjust: Taste the sauce. Adjust seasonings if needed. Want it sweeter? Add a pinch more sugar. Tangier? A tiny splash more rice vinegar. Spicier? Add a pinch of cayenne or a dash of hot sauce. Remember that the flavors will meld and become more pronounced as it chills.
5. Chill: Cover the bowl tightly with plastic wrap or transfer the sauce to an airtight container. Refrigerate for at least 30 minutes before serving. Chilling is crucial – it allows the flavors to fully meld together and deepens the taste significantly. Ideally, make it an hour or even a few hours ahead.

Step 2: Prepare the Chicken

1. Cut the Chicken: If you haven’t already, cut the boneless, skinless chicken breasts or thighs into uniform, bite-sized pieces (about 1-inch cubes). Pat the chicken pieces thoroughly dry with paper towels. Removing excess moisture is key to getting a good sear rather than steaming the chicken.
2. Season (Optional Quick Marinate): Place the dried chicken pieces in a bowl. Add 1 tablespoon of the soy sauce, the minced garlic, grated ginger (if using), black pepper, and salt. Toss gently to coat the chicken evenly. Let it sit for 10-15 minutes at room temperature while you prepare other ingredients or heat the pan. This brief marinating time allows the flavors to start penetrating the chicken.

Step 3: Cook the Chicken

1. Heat the Pan: Place a large skillet, wok, or flat-top griddle over medium-high heat. Allow the pan to get properly hot – this is essential for searing. A cast-iron skillet works exceptionally well here.
2. Add Oil and Butter: Add the 2 tablespoons of high-heat cooking oil to the hot pan. Once the oil shimmers, add the 1 tablespoon of butter. The butter adds flavor and helps with browning, while the oil prevents the butter from burning too quickly. Swirl the pan to coat the bottom evenly.
3. Sear the Chicken: Carefully add the seasoned chicken pieces to the hot pan in a single layer. Do not overcrowd the pan. If necessary, cook the chicken in two batches. Overcrowding lowers the pan temperature and causes the chicken to steam instead of sear. Let the chicken cook undisturbed for 3-4 minutes, until a golden-brown crust forms on the bottom.
4. Stir and Cook: Stir or flip the chicken pieces and continue cooking, stirring occasionally, for another 4-6 minutes, or until the chicken is golden brown on all sides and cooked through (internal temperature should reach 165°F or 74°C). The exact time will depend on the size of the pieces and the heat of your pan.
5. Add Remaining Soy Sauce & Sesame Oil: Once the chicken is cooked, reduce the heat slightly. Add the remaining 2 tablespoons of soy sauce and the 1 teaspoon of toasted sesame oil to the pan. Stir quickly to coat the chicken evenly, letting the sauce bubble and slightly thicken for about 30-60 seconds. Be careful not to burn the garlic or the sauce.
6. Optional Veggies: If adding vegetables like onions, mushrooms, or zucchini, you can either cook them separately and combine them at the end, or push the chicken to one side of the pan after searing and cook the vegetables in the cleared space until tender-crisp, then mix everything together before adding the final soy sauce and sesame oil.

Step 4: Serve

1. Plate the Chicken: Remove the cooked Yum Yum Chicken from the pan and transfer it to serving plates or a platter.
2. Drizzle with Sauce: Retrieve the chilled Yum Yum Sauce from the refrigerator. Give it a quick stir. Drizzle the sauce generously over the hot chicken right before serving.
3. Garnish (Optional): Garnish with sliced green onions or toasted sesame seeds for extra flavor and visual appeal.
4. Serve Immediately: Serve hot with your favorite sides (see “How to Serve” section below).