Cut the green part off the leek and slice the white part in haf lengthwise. Cut into ¾" chunks and separate the pieces. Leeks may contain sand between the leaves so proper washing is important. Wash the leeks thoroughly in a bowl of cold water. Use a slotted spoon to lift the leeks from the water. Do not pour the water off as any sand in the bottom of the bowl with stick back to the leeks.
Drain the leeks on paper towels. Slice the fennel bulb.
Bring 5 cups of water to a full boil. Add the long grain rice and cook for five minutes, then drain.
Melt the butter in a non-stick skillet over low-medium heat. Add the leeks, fennel, salt, and pepper. Cook, stirring frequently until the fennel and leeks are just beginning to soften. Pour in the drained rice and half and half, stirring to combine. Fold in the grated Swiss cheese and pour everything into a buttered casserole dish. Sprinkle a few crushed red pepper flakes over the top.
Bake in a 350 degree oven for one hour. Serve piping hot from the oven.