Preheat the oven to 350 degrees F (175 degrees C). Grease a 10 inch round cake pan.
In a large bowl, stir together the flour, baking powder, baking soda, salt, sugar, and fennel seed. In another bowl, stir together the eggs, buttermilk, and melted butter. Stir the wet ingredients into the flour mixture, until just blended using a large spoon. Spoon the batter into the prepared pan. Dot with the 3 tablespoons of chilled butter.
Bake for about 1 hour in the preheated oven, or until puffed and golden. Cut into wedges and serve warm.