Begin by boiling 2 cups of peeled potatoes in salted water for about 15–20 minutes, or until tender. Once cooked, drain and mash the potatoes until smooth. If using leftover mashed potatoes, ensure they are at room temperature before proceeding. Allow the mashed potatoes to cool completely before combining with the other ingredients.

In a large mixing bowl, combine the cooled mashed potatoes, 4 tablespoons of melted butter, and 1 egg. Utilize a wooden spoon or spatula to mix these ingredients until the mixture becomes smooth and well-combined.

Next, sift in 1 cup of rice flour, ½ cup of corn starch, 1 teaspoon of baking powder, and ½ teaspoon of salt into the potato mixture. Stir gently until a smooth dough forms.

Wrap the dough tightly in plastic wrap and place it in the refrigerator for 30 minutes.

Set your oven to 450°F (230°C) and let it preheat while the dough chills.

Once the dough has chilled, dust a clean surface with rice flour. Divide the dough into 8 equal pieces, rolling each into a ball. Flatten each ball gently until they are approximately ½ inch thick.

In a small mixing bowl, combine 1 tablespoon each of poppy seeds and sesame seeds, along with 1 teaspoon each of dried garlic, dried onion, and dried basil, and a pinch of salt. Mix these ingredients well.

Line a baking sheet with parchment paper and arrange the shaped flatbreads evenly on it. Brush each flatbread with the remaining melted butter, then generously sprinkle the everything topping over the surface. Bake the flatbreads for about 15 minutes, or until they are golden brown and slightly crisp on the edges.