Place the kale and a pinch of salt in a large pan with enough olive oil to fully coat the surface. Cook over high heat for about 3-5 minutes until the kale is bright green and wilted.
Remove from the heat, add lemon zest over top, and once cool enough to handle squeeze the kale with your hands to remove some of the excess water. Add the crumbled feta to the kale.
Place the red potatoes in a bowl and coat them with olive oil and salt. Place the sweet potatoes in another bowl and coat them with olive oil, salt, and chilli powder to taste.
Roll out the chilled dough onto baking paper. Roll out the chilled dough onto the bottom, leaving an inch rim to fold up.
Layer the sliced potatoes on top, alternating between the red and sweet in a concentric pattern. Fold the galette dough up around the potatoes, pinching each turn. Beat 1 egg in a small dish and brush it onto the dough.
Sprinkle coarse sea salt around the rim and drizzle olive oil over the top of the potatoes.
Place into the preheated oven for 20-30 minutes until the potatoes develop a bit of golden brown colour. You can also use a toothpick to see if it easily goes through the potatoes when pricked.
Serve with a fresh salad and enjoy!
