Felted or fleece lined mittens?

I need to make a new pair of mittens for my 2 y/o and last winter I don’t think his plain knit mittens kept his hands very warm. So for this winter I was wondering if you think a felted pair of mittens or a pair of knit mittens with a fleece liner would be warmer?

What about thrummed mittens? I’ve heard those are very warm.

I think the thrummed mittens are a good idea too. It’s almost the same as the fleece lining and as you wash the mittens the thrums felt together inside. Here’s a link to Eunny demonstrating.http://www.knittingdaily.com/blogs/daily/archive/2012/10/31/thrum-pa-pum-pum.aspx in case you’d like to see.

This is one of my favorite knitting blogs. I have learned so much from the Techknitter! She’s from Wisconsin and has two posts just on the subject of “bulletproof” mittens for northern climates. The thrums on these are added AFTER the mittens have been knit. I saw something similar to this adding thrums to the inside with a crochet hook. This may be what she’s doing here. You have to buy her patterns, but they’re only a few dollars.