In a large pot, boil your udon according to package instructions. Drain under cold water, and in the same pot you can cook any vegetables you have. I chose spinach as I had a large bag in my refrigerator.
In a heatproof bowl (this is very important!) combine your garlic, chili powder and sesame seeds. Pour hot oil over these ingredients and stir.
Add your vinegar, soy sauce, sugar and peanut butter (or sesame paste) and stir to combine.
Add your udon noodles and stir to combine.
Top with your desired vegetables - I had cucumber and spinach on hand. Garnish with chili oil (if you like it spicy!) and peanuts.