Gather all your ingredients. Rinse strawberries and blueberries under cool water, then dry briefly. Slice strawberries, thinly slice red onion, and chop fresh basil if using.

In a skillet, melt 2 tablespoons of butter over medium-low heat. Add walnuts and brown sugar, stirring continuously for about 3-4 minutes until fragrant and toasted. Transfer to a parchment-lined baking sheet to cool.

In a small jar or bowl, combine Dijon mustard, honey, and red wine vinegar. Pour in olive oil and add kosher salt. Shake or whisk until emulsified.

In a large salad bowl, layer the base with lettuce mix. Gently fold in half of the sliced strawberries, blueberries, and cooled candied walnuts, then drizzle half of the vinaigrette and toss gently.

Transfer to a serving platter, decorate with remaining strawberries, blueberries, candied walnuts, goat cheese, and drizzle with more vinaigrette.