Kegged Batch Lacks Flavor

I recently kegged a batch of English mild brown ale. After 3 weeks in a keg it still seems to lack much malt flavor. Regardless of the style and how much malt should be tasted, I'm not very happy with it. I would like to try to add some flavor post fermentation and was thinking of using DME to see what it would do. Or I considered doing an addition of raspberries similar to New Belgium's frambozen... Just to add some character. Any suggestions for or against these ideas?

3 weeks in the keg at what temperature? If it has been chilled for that time it just hasn't matured yet. Warm it up so it can mature, then chill it again. Also, don't serve it too cold as the cold masks the flavors.

If you add DME warm fermentation would most likely start again. either way make sure to boil it in some water for at least 20 mins to caramelize. if It's sweetness your missing try boiling a cup or two of brown sugar water and adding it? a fruit addition would add character as well. I'd say first let it condition at room temp for a few weeks and see what happens.

Have you brewed a mild before? When did you keg it? What yeast did you use? Recipe?

I'm beginning to believe that milds - I've brewed 3-4 of them now - really are at their peak young and need to be consumed young to get at their best. Some people have reported that english strains of yeast change character of the beer depending on how/when they are handled and packaged. It's quite possible for the character of a beer to disappear and then reappear later, strange as it may be.

I know that with my last mild, the malt/sugar character was best within a month of brewday, then it declined. The one thing I have to account for is oxidation during transfers and aging. This could also make a beer seem lifeless rather quickly.

Thank you to everyone on the responses! I'm going to take the advice of everyone and pill it from the fridge as its been cold right out of the primary (no secondary). I'll give it some time and retry chilling (at a lower temp) and see what it does. If that doesn't help to my satisfaction, I'll try the DME or fruit addition. Either way patience is the game on this... Lucky to have an APA on tap to hold me over. Thanks again everyone! Love HBT