Four needles to two

How do I convert a mitten pattern from four needles to two needles?

What pattern are you using? Can you link to it or give a name and where you found it? It might be easier to just use a pattern meant for flat knitting.

ETA links:

Simple Mittens (Worked Flat)
Generic Mittens Knit Flat

Some examples.

Yeah it helps if we know the pattern since there are thousands. And I also agree it would be a lot leaguer to find one already written for your needs.

I found the pattern for the Owl Wrist Warmers in Issue Twenty-One of Mollie Makes.

That will be harder so I’ll leave it up to those who know more. Any reason you don’t want to knit in the round?

I think that it would be faster and easier to learn to knit in the round for these. Knitting in the round is great to know, lots of things are faster and easier in the round. That said, there are owl cable patterns for flat knitting so you could try incorporating one of them into flat knit mitts. I strongly suggest that you try knitting in the round.

You can knit them on straight needles and add a stitch to each edge to seam them. The cable crosses would be done on the RS rows and for the WS rows work the sts as they appear - knit the knits and purl the purls. Probably… You could start one and work a few rows past the wrist ribbing and see how it goes.