Heat small non-stick frying pan over medium heat. Add sugar and walnuts. Heat over medium/low heat for 5 minutes stirring frequently so mixture doesn't burn. Let cool.
Mash 2 raspberries and mix with the dijon mustard, white wine vinegar and oil. Add salt and pepper to taste. Tear the salad leaves (wash). Cut the mint leaves in strips. Cut avocado in cubes and sprinkle with lime juice.
Mix the lettuce with half of the dressing and divide over 4 bowls. Divide the avocado, walnuts and the raspberries over each bowl and sprinkle the rest of the dressing and mint on top.