In a saucepan over medium heat, cook the onion and garlic in the oil until they just begin to colour. Season with salt and pepper. Add the tomatoes and bring to a boil. Reduce the heat and simmer gently for about 10 minutes. Add the cream. Adjust the seasoning. Keep warm.
In a bowl, combine the vinegar, oil, garlic, hot pepper flakes and shrimp. Season with salt and pepper. Refrigerate for 15 minutes or longer.
Preheat the grill, setting the burners to high.
Thread a shrimp lengthwise onto the end of each skewer. Grill the shrimp for 1 to 2 minutes per side.
Place the shrimp on a platter and sprinkle with mint. Serve immediately, accompanied by the warm rosée sauce.