This guide is specifically made to speed up the grindy process of getting to 15,000 customers, so here's some recommendations before you start

• Have Platinum Star (for access to new game plus, in new game plus you keep all the customers from your platinum star restaurant.)
  
• Have all 6 pins (if you are planning to go for them), this keeps you from having to do super rush hours with some of the more time consuming foods

Assuming you have both these, and around 6,500 customers, which is about the amount I had gotten when I obtained my Platinum Star (your mileage may vary but that's the number I'll be using.) This will take you approximately 28-31 days only following this method, which will be anywhere from 270-310 customers per day

When starting up New Game Plus you'll want to buy 3 foods immediately:

• Salads (I wouldn't upgrade it but you do you)
  
• Corn Dogs
  
• Pretzels

Coffee and Soda work too but I found those 3 work best for me, you'll only ever need these 3 foods. They all have two things in common, they don't need to be cooked, and can be made very quickly.

Sushi's another option but I don't use it since it can stack negative buzz easily.

Corn Dogs, Pretzels, and Salads done quickly and with enough buzz will continuously keep refilling your customer slots, you'll quickly notice that you've done many many orders by the first super rush hour. The only issues you'll have in the opening days will be your chores.

As for your chores, you'll want to buy all equipment upgrades that have to do with them so you spend less time on them, of course, the first 2 days could be a bit annoying having to keep up with everything but after your upgrades start to come in you should be fine.

The last piece of this is your buzz, which should manage itself for the most part, there's only a couple of notable things to mention

Menu Rot: Menu Rot can be completely ignored to be fair, you'll have at minimum 140% buzz, which is enough to get your 270-310 orders a day, it's just worth mentioning so you don't remove anything from your menu since corn dogs and pretzels are extremely fast to make, the 10% buzz just isn't relevant enough

Extreme Difficulty: On new game plus you're playing on extreme difficulty, which boosts your overall buzz by 50% at all times, giving you the ability to stack buzz very quickly with perfect orders since you already have a 50% base to work with.

Perfect Orders: Your perfect orders are what matters really, it won't be difficult, but you'll want to have at least 200 perfects a day to keep your previous day buzz (100%) and extreme difficulty buzz (50%) at 150%, speaking of 150%

The Soft Cap: There appears to be a soft cap of buzz at 150% for your buzz based off of performance, it's breakable by food buzz boosts such as health nuts, and e-mails with buzz boosts.


Since the soft cap stops your buzz from counting anything over 150%, and you get knocked down by 10% bc of the inevitable menu rot, you'll likely see 140% most days, unless you get an e-mail boost, at most you'll see 160% buzz.

Thank you for reading my guide on this, and I hope this helped you get through what I believe is one of the more grindy achievements out there (doesn't mean I didn't have fun ofc), apparently there was a 20k achievement at one point, let's be thankful that no longer exists.

Hopefully this'll help you get days like this so you can cut down the amount of time you spend: