Step 1 - get yourself a 7qts of mango Goodbelly probiotic juice.
All grain, mash at 148F and sparge to get 50 gallons 1.045 wort. Traditional grist is a mix of pils and wheat, I like a 60-40 split, so about 5# pils and 3.5# white wheat malt.
Extract, use 5# DME for 5 gallons wort. I would probably do 3# pilsner or extra light, and 2# wheat DME.
Collect your wort in the kettle, and either do a short boil (5 minutes) or pasteurize at 170F for about 10 minutes. NO HOPS!
Chill wort to 90F. If you have food-grade lactic acid, adjust kettle pH to 4.4-4.7. This is to keep spoilage bacteria at bay while it sours, as added insurance if your sanitation isn't perfect, and to improve the foam on the final product. If you don't have a pH meter, add around 50ml (1.7oz) 88% lactic acid, maybe 100ml if your water is pretty hard. If you don't have lactic acid on hand, go for the 5 minute boil instead prior to chilling and don't worry about it.
If you want to kill the lacto, once the wort is at 90F, shake up your carton of Goodbelly and dump about half into the wort in the kettle. Seal it up as best you can, and put it aside for 18-24 hours. Don't worry about purging the headspace with CO2, it won't do any good. Let it cool to room temperature.
If you're going to keep the lacto alive, transfer it to your carboy once it's at 90F and add your Goodbelly. Airlock it and set it aside to cool to room temperature.
After 18 to 24 hours at room temperature, taste the soured wort. There should be no krausen, but the wort should be nice and cloudy. It should be sweet but with some tartness, like a lemonade. If you have a pH meter, take a measurement and see if the pH is 3.2-3.5. It should be.
If you left the wort in the kettle, go ahead and finish your boil, go for the full 60 minutes so you don't have any DMS. Chill to ale pitching temperatures, and pitch 18 packets of US-05. You'll need the extra cell count due to the low pH.
If you are not killing the lacto, just add your 18 packets US-05 to the carboy. Don't worry too much about headspace, as you won't get nearly as thick of a krausen with the low pH, but a blow-off tube is never a bad idea.
Fermentation is usually done within 10-14 days. Bottle or keg, it's nice at higher carb levels like 2.7-3.0 volumes.
For a traditional gose, I like 150g sea salt per 50 gallons. This gives you a subtle hint of salt, and you can always add more later. 150g coriander is traditional at flameout.
