Preheat oven to 350. Lightly grease two cookie sheets with butter and set aside.
In a medium-sized bowl, mix first four ingredients and then sift them two times with a flour sifter. To this dry mix, add yogurt, cutting it in with a pastry blender. Set aside.
Melt butter in small saucepan and toast sesame seeds in butter until they start to smell nutty and get a bit browned. Add sesame seeds to dry mix and then ice water. Knead this mixture a bit, perhaps 20 strokes. If dough is still too sticky, add a handful of wheat flour until you can manage to roll it out on a flat surface.
Roll to 1/8 inch thick and cut into desired shapes. Poke many holes into each individual cracker with a fork.
Arrange on cookie sheets with about 1/4 inch between each cracker. Bake for 10 minutes or starting to brown at edges. Cool on baker's rack.