Preheat the oven to 325°F (165°C). Line a large rimmed baking sheet with parchment paper or a silicone baking mat. This lower temperature helps the chestnuts toast without burning the oats.

Mix dry ingredients

In a large mixing bowl combine 3 cups rolled oats, 1 cup roasted coarsely chopped chestnuts, 1/2 cup slivered almonds, 1/4 cup sunflower seeds, 1/4 cup pumpkin seeds, 1/2 cup shredded coconut, 1 tsp ground cinnamon, and 1/2 tsp fine sea salt. Stir until evenly distributed.

Make wet mixture

In a small saucepan over low heat (or in a microwave-safe bowl), combine 1/3 cup maple syrup, 1/4 cup neutral oil, and 2 tbsp packed brown sugar. Warm gently, stirring, until the sugar dissolves and the mixture is glossy (about 2–3 minutes). Remove from heat and stir in 1 tsp vanilla extract.

Combine and coat

Pour the warm wet mixture over the dry ingredients. Using a spatula or wooden spoon, gently fold and press the mixture so the oats and nuts are evenly coated and clumps begin to form. Ensure the chopped chestnuts are well distributed.

Bake and stir

Spread the coated granola in an even layer (about 1/2–3/4 inch thick) on the prepared baking sheet. Bake for 20 minutes at 325°F (165°C). After 10 minutes, remove the sheet and gently stir/turn the granola to promote even browning, then return to the oven for the remaining 10 minutes. Watch the last 5 minutes closely to prevent burning; you want a deep golden color and toasted nuts.

Add coconut and chestnut crisping (optional)

If you prefer the shredded coconut crisp and brown slightly, sprinkle the 1/2 cup coconut evenly over the granola during the final 4–5 minutes of baking. This prevents coconut from browning too early while giving it a toasty finish.

Cool and add dried fruit

Remove the granola from the oven and let it cool completely on the baking sheet (about 30–45 minutes). As it cools it will crisp up and form clusters. Once cooled, stir in 1/2 cup dried cranberries or cherries and 1/4 cup chopped dark chocolate or cacao nibs if using. Taste and add a pinch more salt if desired.

Store

Transfer the cooled granola to an airtight container. Store at room temperature for up to 2 weeks or freeze for up to 3 months. If using chocolate, store in a cool place to avoid melting.