Pre-heat oven to 180°C (160°C fan-forced).
Cook potatoes and celeriac in a saucepan of water until tender. Drain well and mash. Add cream and butter mixing well. Season to taste.
Meanwhile; combine the mustard, rosemary, honey and garlic. Brush a little of the mixture over each cutlet.
Add cutlets to a pre-heated pan and cook over a medium heat for 2 minutes each side until seared. Place on an oven tray, brush with the remaining glaze and cook in the oven for 8-10 minutes, depending on thickness of cutlet. Allow to sit covered for 3 minutes prior to serving with the celeriac mash and zucchini.