That's a lot like a top down shawl or cape. You would start with about 10 sts, knit a row, then increase to double the stitch number. Knit a row, double the stitch number again, then knit a few inches, either increasing 10 sts every other row or 20 every 4 rows, or knit several inches then inc to double the sts again, and keep going until it's the size you want. You can play around with either of these ideas. For an actual shawl pattern that's not really lacy look at the Flower Petal Shawl at elann.com. I made one and it's a lot like half an afghan.