Cut chicken into 1 inch cubes. In large skillet over medium heat, saute chicken in 1 Tb oil, until chicken is lightly browned and cooked through, about 5 minutes; add 1/4 ts salt and pepper. With slotted spoon, remove chicken to large bowl; cool. Remove and reserve pan dripping in skillet. Tear spinach into bite size pieces. Place in bowl with chicken. Add the cut strawberries and onion. In small bowl, stir together vinegar, sugar, poppy seeds, the remaining 2 Tb oil, and the remaining 1/4 ts salt and the reserved pan dripping until well blended. Pour over salad and toss lightly to combine.