At the first level of mastery, your dishes yield 5% more servings (rounded up to the nearest whole number) and are served on a light blue designer plate. (Eg : Bacon Cheeseburger: 13 Servings. Bonus is 5% of 13, which is .65, rounded up to the nearest whole number, 1, so the new number of servings will be 14.)
At the second level of mastery, your dishes rewarded 5% more serving cafe points (rounded up to the nearest whole number) when you serve the dish and are served on a dark blue designer plate. (Eg : Lavish Lamb Curry: 145 cafe points for serving. Bonus is 5% of 145, which is 7.25, rounded up to the nearest whole number, 8, so the new cafe points for serving will be 153.)
At the third level of mastery, your dishes cook 5% faster and are served on a gold designer plate. This bonus is applied after any stove cooking time bonus is applied. For example, Homestyle Pot Roast starts at 48 hours (or 2,880 minutes) to complete. The Cooking Mastery bonus is 5% of 2,880, which is 144, so the new time for cooking will be 2,736 minutes which is 45.6 hours. If there was a 10% stove bonus it would instead first be 10% of 2,880 which is 288 and then 5% of 2,880 - 288 which is another 129.6 (rounds up to 130) leaving us with a total of 2,462 minutes which is 41.03 hours.
You can master a locked dish by clicking on your neighbors' cooking tips (evidence).
Double Mastery was first introduced on May 28, 2011 for Memorial Weekend. It runs till May 30, 2011 to master your dishes 2 times faster.
It was second introduced on August 8, 2011 for Double Mastery Weekend. It runs till August 16, 2011 to master your dishes 2 times faster again.