Preheat waffle maker on medium-high heat. Preheat oven to 200°F (93°C) and place a wire rack on a baking sheet.

In a small saucepan over medium heat, combine 3 cup mixed berries (fresh or frozen), 2 tbsp granulated sugar or honey, and 1 tbsp lemon juice. Cook, stirring occasionally, until berries break down and juices thicken slightly. ⏱ 10m

If using, stir in 1 tsp cornstarch (optional, for a thicker compote) slurry and simmer 1-2 more minutes until glossy and thickened. Remove from heat and set aside.

In a large bowl, whisk together 1 ½ cup whole wheat flour, ½ cup oat flour (blitzed rolled oats), 2 tbsp ground flaxseed, 1 tbsp baking powder, ½ tsp ground cinnamon, and ¼ tsp salt. Set aside.

In another large bowl, whisk together 6 tbsp neutral oil or melted coconut oil, 2 large eggs, room temperature, and 2 tbsp packed brown sugar. Whisk in 1.8 cup buttermilk and 1 tsp pure vanilla extract until combined.

Pour the wet ingredients into the dry ingredients and whisk gently until just combined. Some small lumps are fine — do not over-mix.

Grease the preheated waffle maker. Pour about ⅓ cup of batter into each well (adjust for your waffle maker's size) and close the lid.

Cook until crisp and golden, following your waffle maker's instructions. ⏱ 5m

Transfer cooked waffles to the wire rack in the warm oven while you cook the remaining batter.

Serve waffles warm, topped generously with the mixed berry compote.