Prepare the Vegetables: Thinly slice half an onion, three green onions (keeping whites and greens separate), smash and finely chop two cloves of garlic, and cut one cucumber into thin matchsticks.
Make the Sauce: In a small container, mix 1 tbsp of Chinese chili bean paste, 2 tbsps of peanut butter, 1 tbsp of soy sauce, 1 tbsp of vinegar, and 1 tbsp of chicken bouillon powder.
Cook the Noodles: Cook two servings of spaghetti noodles in boiling water until al dente. No need to season the water with salt.
Build the Creamy Tantan Sauce: In a large pan, heat 1 tbsp of chili oil and half a tablespoon of neutral oil over medium-high heat. Add the onions, green onions, and garlic, sautéing for about 2 minutes. Reduce heat to low, add the sauce mixture, and stir for about 1 minute. Then add one cup of heavy cream, stir, and simmer for about 3 minutes.
Combine Noodles and Sauce: Add the cooked noodles to the sauce in the pan, mixing well for about 2 minutes or until they're nicely coated.
Serve: Plate the noodles, topping them with cucumber matchsticks, green onions, and optionally, chili oil or Sichuan peppercorn oil for extra heat. For a fancy touch, sprinkle with crushed peanuts or any nuts you like.