Roasted Chestnut-Sweet Potato Thai Moon Cookies

What Makes This Special

This cookie adapts a Thai-style shortbread (khanom ping) with a seasonal chestnut-sweet potato filling and autumnal colors, shaped with mooncake molds for structure and visual definition. The roasted chestnut and coconut cream filling mimics the texture of traditional mung bean paste used in Thai cookies but introduces earthiness and subtle sweetness. Roasting builds depth and comfort; the orange sweet potato adds color and a starchy, tender crumb.

Ingredients

Each ingredient has a direct function—rice flour for the fragile, sandy texture; chestnuts and sweet potato for filling structure and color; coconut cream for richness; butter and oil for the melt-in-mouth crumb; salted egg for umami and structure.

For the Chestnut–Sweet Potato Filling

• Roasted chestnuts, peeled – 120g
• Orange sweet potato, peeled – 100g
• Coconut cream – 50ml
• Granulated sugar – 40g
• Fine sea salt – 1g

For the Dough

• Rice flour – 140g
• Wheat flour (plain) – 80g
• Icing sugar – 60g
• Fine sea salt – 1g
• Salted egg yolks, cooked – 2 (about 30g total)
• Unsalted butter, softened – 90g
• Vegetable oil – 30ml

For Finishing

• Egg yolk, for egg wash – 1
• Water – 10ml
• Sesame seeds, toasted (optional) – 1 tbsp

Instructions

Step 1: Roast the Chestnuts and Sweet Potato

Preheat oven to 200°C. Place chestnuts (in their shells) on a tray, roast for 25 minutes or until visibly cracking. Peel while warm. Wrap sweet potato in foil and roast simultaneously until very soft, about 40 minutes. Roasting drives off excess water, deepens flavor, and ensures a dry filling that will not collapse the cookie exterior.

Step 2: Prepare the Filling

Blend roasted chestnuts and roasted sweet potato in a food processor until smooth. Add coconut cream, sugar, and salt. Cook this paste over low heat in a saucepan, stirring constantly, until thick and cohesive, about 8–12 minutes. The goal is a thick, almost dough-like paste that holds its shape. Cool completely before forming.

Step 3: Form Filling Balls

Divide cooled filling into 16 portions (about 15g each). Roll into balls. Chill until needed. Chilling sets the filling structure, making molding easier.

Step 4: Make Cookie Dough Base

Sift rice flour, wheat flour, icing sugar, and salt into a large bowl. Rub in cooked salted egg yolks until a fine crumb forms—this is essential for the sandy Thai-style texture. Add softened butter and oil. Mix gently with fingers or spatula until a soft, pliable dough forms. Do not overwork or gluten will develop, toughening the finished cookie.

Step 5: Portion and Wrap

Divide dough into 16 pieces (about 22g each). Flatten each piece into a disc. Place a filling ball in the center and wrap dough around it, sealing completely. Roll gently to smooth. Dough will be delicate; patch cracks with extra dough if needed.

Step 6: Mold and Shape

Lightly flour mooncake or decorative cookie molds. Press each ball gently into the mold to imprint the design, then tap or push out. Uniform pressure prevents cracks and gives clean definition. Place on a lined tray.

Step 7: Bake

Preheat oven to 170°C. Bake cookies for 10 minutes. Remove, brush lightly with beaten egg yolk-water wash, and if desired, sprinkle with sesame seeds. Bake an additional 8–10 minutes, until the surface is matte and lightly golden. Do not overbake; the cookies should remain pale with a faint orange hue. Cooling firms structure; do not move until set.

Step 8: Cool and Store

Cool completely on a wire rack; the shells are fragile when hot. Texture improves after 1 day as moisture redistributes.

Pro Tips

• Roasting removes excess moisture and prevents soggy filling.
• Rice flour is non-negotiable for the characteristic sandy crumb; do not substitute.
• Cooling is critical—moving while hot will shatter the shells.

Troubleshooting

Filling leaks during baking? Filling was too wet. Cook longer in step 2 to evaporate more water.

Cookie shells cracking in the mold? Dough is too dry or too cold. Knead gently to rehydrate or let warm slightly before molding.

Dough sticks to mold? Insufficient flouring or dough too wet. Flour molds thoroughly between each cookie.

Variations

• Substitute taro or purple sweet potato for a different autumn color.
• Add pandan paste to the dough for herbal notes (green color, not autumnal).
• Omit salted egg yolk for a more neutral flavor; increase butter by 15g to compensate for fat loss.

Storage

Store airtight at room temperature for up to 5 days. Texture is best on day 2. Do not refrigerate; moisture will degrade the shell.