Source: Good Eats, Alton Brown, Food Network
| 1 1/2 | cups | sour cream | 
| 3/4 | cups | mayo | 
| 2 | tbsp | olive oil | 
| 1 1/2 | cups | onions, diced | 
| 1/4 and 1/2 | tsp | kosher salt (used on two occasions) | 
| 1/4 | tsp | white pepper | 
| 1/4 | tsp | garlic powder | 
Why cook onions for so long? - 1) remove excess moisture, 2) caramelize the sugar in them, 3) create dark color for the dip
Why not black pepper? Because AB thinks it would make the dip look bad.