Nicole & Joel's Domestic Bliss!

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Move over Rachael Ray, there's another cute cook in the kitchen! The Simple Life star Nicole Richie took up cooking in order to become the perfect partner and mom. Now, she's gotten so good at it she wants to publish her own cookbook!

"She keeps a box full of recipes handwritten on index cards," a pal of Nicole,26, tells OK!. "She has mac and cheese down to a fine science!"

But when it comes to whipping up meals for fiance Joel Madden,29, Nicole, who is mom to their 5-month old daughter Harlow, looks to the lighter side.

Says the source, "She keeps things low-fat to help her and Joel watch their weight!"