1. The Greens: Start by washing and thoroughly drying your greens. I cannot emphasize this enough—wet lettuce dilutes your dressing. Use a salad spinner or a clean kitchen towel. You want crisp, dry leaves that act as a proper vessel for the vinaigrette.
2. Shredding the Chicken: While your chicken breasts are still warm from poaching or baking, use two forks to pull the meat into delicate, bite-sized ribbons. Working while warm is non-negotiable; the fibers relax and absorb the dressing, turning the chicken from a bland protein into the star of the dish.
3. The Emulsion: In a small glass jar or bowl, combine your olive oil, lemon juice, mustard, salt, and pepper. Whisk vigorously until the mixture looks thick and creamy. This is an emulsified dressing, meaning it will cling to the salad rather than pooling at the bottom of the bowl.
4. The Assembly: In a large mixing bowl, combine the greens, tomatoes, cucumber, and red onion. Drizzle with half the dressing and toss gently with your hands or tongs. Add the shredded chicken, drizzle the remaining dressing, and top with the pumpkin seeds for a final, nutty crunch.

I am a firm believer that the only way to stay consistent with healthy eating is to make it convenient. You can poach and shred your chicken at the start of the week. Store it in an airtight container for up to three days. Keep your dressing in a separate small jar in the fridge; just remember to give it a quick shake before serving, as the emulsion may settle.

If you want to pack this for work, place the dressing at the bottom of your container, followed by the hardier vegetables like cucumber, then the chicken, and finally the greens on top. This "vertical layering" keeps everything crisp until you are ready to shake and eat.