Make the poached chicken. Lay the chicken on the bottom of medium (4-quart) pot. Cover with cold water by 2” and add 1 tbsp salt; if you're using additional aromatics, add them now (see post notes). Heat over high until boiling. Reduce heat to medium, adjusting heat to maintain a simmer. Simmer an additional 8-10 minutes, or until chicken reaches 165°F on an instant read thermometer. Drain, rinse under cool running water to stop the cooking process, then set aside under cool enough to handle. Dice into 1” bite sized pieces.
Make the citrus supremes. Using a sharp paring knife, slice off the top and bottom of the orange. Stand the fruit upright on a cutting board. Slice off the skin and pith from top to bottom, following the curve of the fruit. Carefully slice along the membrane line on either side of a section to release the fruit in a neat, even slice. Repeat this process until each section has been sliced.
Place a strainer of a medium sized bowl. Squeeze each orange membrane over the strainer to juice.
Place the diced poached chicken, citrus supremes, endive, spinach, and avocado into a large mixing bowl. Toss to combine. Divide the salad into meal prep bowls and top with 1 tbsp almonds each.
Make the vinaigrette. Combine three tablespoons of fresh squeezed orange juice with the vinegar, whole grain mustard, salt, and pepper. Whisk until combined. Pour in the olive oil in a steady stream while whisking vigorously. Continue to whisk until the dressing is emulsified, then portion into small containers. Pack a container of dressing with each salad.
When you’re ready to serve, pour the vinaigrette over the salad, toss, and dive in. These meal prep bowls keep in the fridge for up to three days.
To prevent the avocados from browning, toss with a small amount of the reserved orange juice. The acidity should keep them fresh for an additional 1-2 days.
Substitute 2 cups leftover roasted chicken for the poached chicken.