Place the chicken breast between two sheets of parchment paper and pound to an even 1/2-inch thickness for uniform cooking.
Place the chicken in a shallow bowl and pour the buttermilk over it, ensuring it is fully coated; let it marinate for 10 minutes.
In a separate shallow dish, whisk together the whole wheat flour, smoked paprika, garlic powder, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting any excess liquid drip off, then dredge thoroughly in the flour mixture until evenly coated.
Heat the avocado oil in a non-stick skillet over medium heat until shimmering.
Add the chicken to the skillet and cook for 5-6 minutes per side until the exterior is golden brown and the internal temperature reaches 165°F.
While the chicken cooks, lightly toast the sprouted grain bun in a toaster or on a separate dry pan until warm.
Assemble the sandwich by placing the romaine lettuce on the bottom bun, followed by the crispy chicken and the dill pickles.