1. Melt the butter in a large, deep pan over medium heat. When the butter foams up, add the sliced red onions and simmer until they are tender and transparent.
2. Chop the strawberries and combine the sugar with the vinegar and red wine. Add the chopped strawberries and the sugar-vinegar mixture to the red onions. Turn up the heat and continue to cook until the liquid has reduced and evaporated.
3. Add salt, pepper and fresh thyme to the ground meat and mix well. Shape into sliders (approx. 120g each). Melt the butter and oil in a pan over medium heat and fry the sliders for 2 min. on each side.
4. Spread the homemade aioli on a slider or burger bun and top with fresh arugula which gives the burger a peppery flavour.
5. Top with Castello® Burger Blue, either cold or melted! Creamy and delicious :)
Serve with crisps or a fresh summer salad.