In a small bowl, whisk together the balsamic vinegar, honey, minced garlic, thyme, salt, and pepper. Set the marinade aside.
Place the chicken breasts in a resealable bag or shallow dish and pour half of the marinade over the chicken. Allow it to marinate in the refrigerator for at least 30 minutes (or up to 2 hours for more flavor).
Preheat your grill or a skillet over medium-high heat. Heat the olive oil in the skillet if using.
Remove the chicken from the marinade and discard the leftover marinade. Grill or sear the chicken for about 5-7 minutes on each side, or until the internal temperature reaches 165°F (75°C).
While the chicken is cooking, add the sliced strawberries to the remaining marinade in a saucepan. Bring it to a simmer over medium heat and cook for about 5 minutes, or until the strawberries soften and the sauce slightly thickens.
Once the chicken is cooked through, remove it from the heat and let it rest for a few minutes.
To serve, place the chicken on plates and spoon the strawberry balsamic mixture over the top. Garnish with fresh basil leaves if desired.
Notes
For best flavor, marinate the chicken for up to 2 hours.