1. In a bowl, add the balsamic vinegar, 1/2 cup of olive oil, rosemary and mix together.
2. Submerge the sirloin steak in the marinade and let it cool for 30 minutes.
3. Slice the Yukon potatoes and put them in water so they don't turn brown.
4. In a first pan, add a teaspoon of olive oil and caramelize the potatoes and onions.
5. In a second pan, cook the bacon. Once crispy, add the mushrooms and garlic and mix.
6. When the potatoes are almost cooked, add the contents of the second pan into the first pan and mix well.
7. Add in cream and adjust salt and pepper.
8. Remove the sirloin from the fridge and season with salt and pepper.
9. Grill the sirloin for 3-4 minutes on each side.
10. Plate the potato hash and place the sirloin steak on top. Garnish with thyme and serve.