Preheat the oven to 180*C/375*F.
Remove any old and tatty looking leaves from the outside of your head of cabbage. Cut it into quarters and remove the core. Shred coarsely.
Trim the leeks, cut in half and wash them thoroughly. Shred them coarsely as well. Mix them into the cabbage.
Bring a large pot of lightly salted water to the boil. Add the vegetables. Bring back to the boil, and then reduce the heat to a simmer and cook them for about 5 to 6 minutes, just until barely tender. Drain in a colander. Make sure you get as much water out as you can. You don't want any to dilute the delicious cream sauce.
Make your cream sauce by melting the 3 TBS of butter in a saucepan. Stir in the flour and cook, stirring over medium heat, for about one minute. Slowly whisk in the milk and cook, whisking constantly, until smooth and nicely thickened. Season to taste with some salt, pepper and grated nutmeg. Add a splash of hot pepper sauce to taste.
Put the cabbage mixture into a buttered shallow dish. Pour the cream sauce over top and allow it to soak in for a few minutes, while you make the crumbs for on top
Melt the 2 TBS of butter and then stir in the bread crumbs, mixing all together well. Sprinkle the buttered crumbs evenly over the top of the casserole. Bake in the preheated oven for 25 to 30 minutes, until nicely bubbling and the crumbs are lightly browned on top.
Note - I sometimes add a cup of grated gruyere cheese, plus 1 heaping TBS of grated Parmesan cheese to the sauce to give it a rich and cheesy flavour. You may also add some grated cheese on top if you wish.