Make the dressing: In a small jar, whisk or shake together olive oil, lime juice, honey, Dijon, salt, pepper, and poppy seeds if using. Taste and adjust sweetness or acidity.
Prep the berries: Rinse gently and pat dry.
Slice strawberries. Keep raspberries and blackberries whole to avoid mushiness.
Toast the nuts: Warm a dry skillet over medium heat and toast almonds or pistachios for 2–3 minutes until fragrant. Let cool.
Build the base: Add greens to a large bowl or platter.
Sprinkle in mint for a fresh lift.
Add the berries: Scatter strawberries, blueberries, raspberries, and blackberries evenly over the greens.
Top with extras: Add crumbled feta or goat cheese, toasted nuts, and avocado if using.
Dress and toss: Drizzle about half the dressing over the salad. Gently toss to coat without crushing the berries. Add more dressing as needed.
Finish and serve: Taste, adjust salt and pepper, and garnish with extra mint.
Serve right away.