In large pot of boiling water, cook cauliflower, carrots and celery for 7 minutes or until tender crisp. Drain and set aside.
In the same pot, melt butter with oil over medium heat. Cook onions and garlic for 4 minutes or until onions are softened. Stir in flour, mustard and pepper. Cook, stirring, for 1 minute.
Gradually stir in chicken stock. Bring to boil. Reduce heat and simmer for 2 minutes or until thickened, stirring frequently. Stir in milk. Add ham, cauliflower, carrots and celery. Spoon the mixture into a shallow casserole.
Combine cracker crumbs, edam cheese, almonds and parmesan. Sprinkle over casserole. Bake, uncovered, for 30 to 40 minutes or until heated through and top is golden brown.