Cook Potatos. Place water 1/2 full in 4 litre pot, set heat to high.
Wash potatoes, keep skin on; cut in half lengthwise and cut crosswise, 1/3" thick.
When water is boiling add potatoes and cook until firm, not too soft, approximately 20 minutes Remove from heat, remove potatos and allow to cool. Retain 1/2 cup of water for roux (see below).
Make Bechamel Sauce. While potatos are cooking combine butter and flour in medium size saucepan set to low heat. Whisk butter and flour together. Slowly add milk while whisking rigorously. Add 1/2 cup of potato water. Be sure liquid is incorporated into roux before adding more. Add nutmeg, celeriac, bay leaf and pepper. Cook overlow heat for 15 minutes. Add parmesan and remove from heat.
Sear Ham Steak & Make Red Wine Reduction. Cook ham in pan set to medium high heat, 3 minutes each side. Set ham aside, set heat to low, add red wine and bay leaf, turn off heat. While wine reduces cut ham, including fat, into 1/4" pieces.
Combine potatos, ham, garlic and parmesan in casserole dish and drown in bechamel sauce. Cook in oven preheated to 350 degrees, covered, for 2 hours. In last ten minutes add grated cheese and love oil and set under medium broiler for 5-10 minutes, or until golden coloured.
Serve while bubbling.