In a small bowl or a jar with a tight-fitting lid, whisk together the fresh lemon juice, extra virgin olive oil, Dijon mustard, and honey (or maple syrup).
Add a good pinch of salt and pepper. Whisk vigorously until everything is well combined and looks slightly creamy. If using a jar, just pop on the lid and give it a good shake!
Taste the dressing and adjust seasoning if needed – maybe a tiny bit more honey if your berries are tart, or more salt to bring out the flavors.
In a large salad bowl, place your mixed greens.
Halve the avocados, remove the pits, and scoop out the flesh. Slice or dice the avocado into bite-sized pieces and gently add them to the bowl.
Add the fresh blackberries, thin slices of red onion, pecans, and crumbled goat cheese to the bowl with the greens and avocado.
Right before you're ready to serve, drizzle the desired amount of dressing over the salad ingredients. Start with less than you think you'll need, as you can always add more!
Using two large spoons or salad tongs, gently toss everything together until the greens and other ingredients are lightly coated in the dressing. Be careful not to smash the delicate berries and avocado.
Garnish with fresh herbs if you have them.
Serve immediately.