If you grind your own flax seeds in a blender, try putting the poppy seeds in with them. If you don't have a springform pan, use a round cake pan and follow the pan preparation instructions. I feel pretty certain that it would work just fine. I got my hazelnuts (also known as filberts) from Freddy Guy's in Oregon. They are fabulous!Someone asked me if this cake is "healthy." Well, yes, for a dessert. It offers healthy fats, anti-oxidants from the chocolate, is low on the glycemic index, and also offers protein and fiber. But it's still a special treat, as it's a calorie-dense food. In that same category are some other healthy(ish) birthday cake ideas: Rosemary and Olive Oil cake from Domestic Divas Gluten-free lemon almond polenta cake from A Food Centric Life (I have had this and it is g-o-o-d!) Vegan chocolate cake with chocolate hazelnut ganache from What Would Cathy Eat?