If using fresh wide rice noodles, separate them gently with your fingers. If they are cold and stuck together, warm them in the microwave for a few seconds, or steam them very lightly, just until they loosen and peel apart. If using dried wide rice noodles, soak or boil them according to the package until just tender but still slightly chewy, then drain well. You need about 800g cooked noodles in total. If they start to stick, toss them with a few drops of neutral oil, but never coat them heavily. The noodles should be soft, pliable and fully separated before cooking begins. That separation is what lets the noodles stir-fry evenly, since cold, clumped noodles break apart and colour unevenly once they hit the wok.

Place the 800g sliced beef in a bowl and add the 1 tbsp oyster sauce, 2 tsp light soy sauce, 1 tsp fish sauce, 1 tsp neutral oil, 1 tsp cornstarch and ¼ tsp white pepper. Mix thoroughly until every slice is evenly coated and no dry cornstarch remains visible. Let it stand for 10–15 minutes. The slices should look lightly glossy rather than wet; if a little liquid gathers at the bottom of the bowl, stir it back through just before cooking so it clings to the meat. That light marinade is what seasons the beef, while the thin cornstarch coating genuinely protects it during the very fast, high-heat sear so the slices stay tender.

In a small bowl, stir together the 60ml oyster sauce, 45ml light soy sauce, 15ml dark soy sauce, 30ml fish sauce, 2 tsp sugar and 2 tbsp of the water. Keep stirring until the sugar has dissolved completely. Taste it: the sauce should be savoury, salty, slightly sweet and fairly strong on its own. If it tastes harsh or too thick to pour easily, add the remaining 1 tbsp water. The dark soy should deepen the colour without dominating the other flavours. Set the bowl beside the stove. That deliberately strong seasoning is what lets one batch of sauce flavour 800g of noodles, as well as the beef and vegetables, without the finished dish tasting flat.

Finely chop or pound the 6 garlic cloves. Slice or roughly pound the 6–10 bird's eye chillies, adjusting the number to your heat tolerance, and slice the mild red chillies, if using. Cut the onion into wedges or thick slices and slice the red and green bell peppers into strips of a similar width so they cook at the same rate. Pick the 40–50g Thai basil leaves from their stems, and set the small handful of finishing leaves and any extra sliced chillies aside separately. Arrange everything beside the stove with the marinated beef, the sauce, the noodles and the oil. That complete setup matters because pad kee mao cooks in minutes, leaving genuinely no time for slicing or measuring once the wok is hot.

Heat a wok or large heavy pan over high heat until very hot and just beginning to smoke. Add 1 tbsp of the neutral oil and swirl to coat. Lay half the beef in a single layer and sear for 45–90 seconds, tossing only as needed, until the outside is browned but the meat is not fully cooked through. Remove it to a plate, then repeat with another 1 tbsp oil and the remaining beef. If the slices release liquid and turn grey instead of browning, the pan is crowded or not hot enough, so let it recover before adding more. That brief, genuinely hot sear is what browns the beef while keeping it tender and slightly juicy, since it returns to the wok later.

Keep the wok over high heat, lowering it slightly only if it is smoking excessively. Add the remaining 1–2 tbsp neutral oil, then the garlic and bird's eye chillies, and stir-fry for 10–15 seconds, until intensely fragrant but not browned. Add the onion, bell peppers and mild red chillies, if using, and stir-fry for 1–2 minutes, until slightly softened at the edges but still bright and holding their shape. The peppers should keep a little bite rather than turning limp. If the garlic starts to darken before the vegetables go in, add them immediately to cool the pan. That short, hot stir-fry is what keeps the vegetables distinct and colourful against the soft noodles instead of collapsing into them.

Add the 800g noodles to the wok and pour the sauce over them. Using tongs, chopsticks or a wide spatula, lift and turn the noodles gently so they coat evenly without tearing. Between tosses, let portions of the noodles sit against the hot wok for a few seconds so they develop slight caramelised, stir-fried edges. Cook for about 1–2 minutes, until the noodles are glossy, hot and evenly brown. The sauce should coat the noodles rather than pool at the bottom of the wok. If it looks watery, the heat is too low or the pan is overcrowded; with a smaller wok, fry the vegetables, noodles and sauce in 2 batches rather than forcing everything into one pan. That brief contact with the hot metal is what gives drunken noodles their lightly charred, genuinely smoky edges.

Return the seared beef and any resting juices to the wok. Toss everything together for 30–60 seconds, until the beef is heated through and evenly mixed through the noodles and vegetables. Add the 40–50g Thai basil leaves and toss just until they wilt into the hot noodles, which takes only a few seconds. Remove the wok from the heat immediately. The basil should look glossy and bright green rather than dark or slimy, and the beef should still be tender and juicy rather than dry. That last-second addition is what preserves the Thai basil's fresh, peppery aroma, because cooking it any longer turns the leaves dark and flattens their flavour.

Divide the noodles between 4 bowls, about 200g of noodles and a quarter of the beef in each, with an even share of the onion and peppers. Top each bowl lightly with a few of the reserved fresh Thai basil leaves and, if desired, a few extra sliced chillies. Serve immediately, while the noodles are still hot, glossy and slippery. The finished dish should be lightly sauced, with tender beef, still-distinct vegetables and visible basil throughout, and no pool of sauce at the bottom of the bowl. If the noodles look dry, they spent too long in the pan, so pull the next batch sooner. That immediate serving is what keeps the noodles slippery and the basil fragrant, since both dull quickly as the dish cools.