Rinse 1 pound of fresh strawberries under cool running water for 30 seconds. Pat them completely dry with paper towels (this prevents excess moisture). Remove the green stems and slice strawberries into quarters or halves depending on their size. Set aside in a bowl.
In a small bowl, whisk together 2 tablespoons balsamic vinegar, 1 tablespoon honey, and 1 teaspoon Dijon mustard for 1 minute with a small whisk or fork until fully combined.
Slowly drizzle in 3 tablespoons extra virgin olive oil while whisking constantly for 2–3 minutes, whisking vigorously until the mixture looks creamy and light (this is emulsification). Checkpoint: Your vinaigrette should coat the back of a spoon and not separate immediately when you tilt the bowl.
Taste the vinaigrette and add a pinch of salt and black pepper. Adjust honey or vinegar to your preference (it should taste balanced—not too tart, not too sweet).
Add 5 ounces of baby spinach to a large mixing bowl or salad bowl.
Pour the warm vinaigrette over the spinach and toss gently with salad tongs for 30–45 seconds until the leaves are evenly coated and slightly wilted (they should darken a little but still hold their shape). Checkpoint: Every leaf should glisten with dressing.
Gently fold in the sliced strawberries (about 1 pound) and a thin slice of red onion (about 1/4 onion, thinly sliced) into the dressed spinach. Toss very gently for 10–15 seconds to avoid bruising the berries.
Divide the salad evenly among 4 serving plates (about 2 cups per plate).
Top each plate with 1 ounce crumbled goat cheese (roughly 2 tablespoons per plate, crumbled by hand into small, irregular pieces). Checkpoint: Cheese should be visibly distributed across the surface.
Sprinkle 2 tablespoons candied pecans (crushed into bite-sized pieces) over each serving. Some pecans should be whole, some broken.
Serve immediately while the spinach is still slightly warm (within 2–3 minutes of assembly). If you wait too long, the greens will wilt too much and the salad becomes soggy.
If making this ahead: Keep spinach and dressing separate in the refrigerator for up to 4 hours. Assemble just before serving.