This pattern can be found in my 2016 book Double or Nothing: Reversible Knitting for the Adventurous.
I do like to add my own style to things, so I’ve done these mittens a little differently from your average pair (and I don’t just mean the double-knitting). You may notice that the fingertips are not centered -- they instead center roughly on the middle finger, which is usually longest. In addition, they use the Eastern Thumb, which I feel is sorely in need of more exposure in mitten patterns. There’s also a really neat trick used to seam the fingertip, thumb tip and gusset.
Each medium-sized mitten takes approximately 20 g of each yarn or 40 g total, so 1 pair is 80 g. A large mitten is less than 20% larger so it should be possible to get 2 large mittens out of 100 g of yarn. However, better safe than sorry: buy 2 balls of each just in case.