Trim kangaroo of sinew and halve lengthwise. Reserve trimmings for later. Season olive oil with salt and pepper. Rub over each fillet, then cover and chill for 1 hour.
Start Shiraz Butter sauce and set aside.
Preheat oven to 200°C.
Heat a non-stick frying pan over high heat and seal fillets on both sides quickly, until browned. Transfer to a oven-proof pan and roast for 8 minutes. Remove from oven, cover with tin foil and let rest about 10 minutes in a warm place.
Meanwhile , melt the butter in a frying pan until it starts to foam slightly. Add spinach in all at once. As it starts to wilt add lemon juice and season to taste.
Mound spinach onto warm serving plates, top with sliced kangaroo. Spoon sauce around and drizzle a bit over the steak.
Shiraz Butter Sauce: Melt butter and oil in a wide suace pan. Add vegetables and meat trimmings. Stir over medium heat for 5 minutes. Add wine, stock, water and simmer for 20 minutes or until only about 1/2 cup liquid remains. Strain and set aside.
Once fillets come out of the oven, heat the reserved sauce and add cooking juices from roasting pan. Whisk in the extra butter slowly until emulsified.