What kind of chocolates are used to make the lava-cookies?  How can i keep it in liquid state inside the cookies?  Thank you.  ps. Sorry, my English is as bad as my baking skill. 
The only way that I know to get them to have a near-liquid center would be to either warm them back up, or to use something that's already liquid at room temperature.  I don't know if I would recommend this to someone without much baking experience, but for someone comfortable with baking and who wants to experiment ... I'd try the following.  (note, this is pure conjecture, I've never done this myself) :   Make a fudge sauce that's liquid (or at least gooey) at room temperature Chill it enough so that you can shape it, or find some molds of a decent size Pipe it out onto a chilled sheet tray to make blobs of your intended size Make your cookie dough, and chill it down. Assemble the cookies and bake them.   ... it's quite possible that they won't keep for very long without chilling them (so you'd have to let them sit out to get back to liquid again, or warm them up through some other means).  Also possibly of interest -- I've found that letting a container of chocolate chip cookies sit in a closed car for an hour or two brings them back to that just-slightly-melted quality that you get from fresh baked cookies. 