1. Put the bacon slices in a cool pan and fry until crispy. Pour off the fat and set aside to cool. Remove the bacon and let it drip off on some paper towels, then finely chop.
2. Beat the egg yolks with the mustard and white wine vinegar. Add the oil and bacon fat very slowly, whisking constantly.
3. Stir in the bacon and season to taste with salt and pepper. Peel and slice the onions and fry them in butter. Add the sugar and let it melt. Stir in the wine and add the sprigs of thyme. Cook off the wine for approx. 15 min.
4. Peel the onion for the cucumber salad. Thinly slice the onion and the cucumber. Combine the lemon juice, oil, rose pepper and salt. Pour the dressing over the onion and cucumber slices and stir gently.
5. Form the ground meat into four patties. Sprinkle with salt and pepper, brush lightly with oil and barbecue for 2-3 min. on each side. Top with the a slice of Castello® Burger Blue cheese and let melt.
6. Toast the buns sliced-side down. Top each bun with a burger, bacon-mayo, cucumber salad and onions in port.