title_body: Getting large volume lattes
upvoted_answer: Assuming you are not planning to buy a lot more machinery, you can simply use the Nespresso to make espresso - depending on your preferred strength, two to three shots should be what you need for your 20 oz mug. A Starbucks “Venti” is named for the twenty oz volume and contains three shots. 
  
  But that's basically a puddle in your mug:
  You need to fill the other 16 oz. and you do that with steamed (foamy) milk. If you wanted to do this "correctly", you would use the steam wand of your espresso machine - which the Nespresso doesn't have, I presume.   
  
  
  If you have an immersion blender, preferably with a disk, heat (not boil!) your milk and whizz it until you get soft foam.   
  Other options are a stovetop or electric milk frother - the manual pump-action ones are available for the price of four to five Starbucks coffees, the electric ones cost a bit more. 
  Do not buy one of these teeny-tiny hand-held flimsy wire-whisk stirrers, they are a funny gadget but not sturdy enough for daily use and large volumes of milk.
  
  
  The milk-to-foam-to-espresso ratio is up to you, find what you like best. I suggest starting somewhere at about two thirds milk / one third foam plus three shots and tweak your drink until you find your preferred recipe.
  
  For more inspiration, see this answer over at Seasoned Advice.