0.9L Evernew Ti, for 3-season solo trips. I don't cook in bags; I boil my 500ml/2 cups of water, then dump food into pot, stir, and turn stove off. I would boil over in a smaller pot. In the morning I boil 700ml, some for coffee, poured off, then rest for oatmeal/cherries. I have boiled over w/oatmeal in this pot. Why do I "cook" in the pot? Super-easy clean up, super-clean eating, and I don't have to carry a grimy, slimy, smelly, heavier bag in my pack.
For winter I use a 2L pot for melting snow. Honestly, I find an even larger pot more convenient... mold up big bricks of snow, toss 'em in, and get a goodly amount of hot "seed" water going. Especially nice w/getting water for the 2 dogs and I, and maybe a friend. I'm playing with a cheapo ~7 oz 4L aluminum pot for this winter.