Heat two teaspoons olive oil in a non-stick pan, add kale, garlic and salt, mix well and cook till kale is soft and garlic is fragrant.
Add corn kernels and cook, stirring for two minutes. Transfer the mixture into a bowl and cool. Add cheese and mix well.
Cut the chicken breasts horizontally into two parts. Insert a thin paring knife into the thickest part of the chicken breast and cut down the side to make a three inch pocket. Repeat with the remaining chicken breast.
Stuff kale mixture into the chicken breasts.
Heat another non-stick pan.
Rub the stuffed chicken breasts with the remaining oil and sprinkle salt and crushed peppercorns on them.
Place chicken breasts in the pan and cook on low heat till the chicken is fully done and is golden from both sides.
Transfer the chicken onto a serving plate.
Combine chicken stock and flour in a bowl, mix well and add to the same pan. Mix and cook till the sauce thickens, scraping off all remaining bits of the chicken.
Remove from heat, stir in lemon juice and add salt and crushed peppercorns. Mix well.
Pour the sauce over the stuffed chicken breasts and serve hot.