Prepare an 8-inch square baking pan by greasing it lightly and lining it with parchment paper.
In a large mixing bowl, combine the eggs, palm sugar, and salt. Beat on high speed for about 10 minutes, until the mixture becomes pale, thick, and fluffy. The batter should fall back into the bowl in ribbons and leave a visible trail.
Sift together the flour, milk powder, spekkoek spice mix, and ground cinnamon, then add them to the batter.
Using a spatula, gently but quickly fold the dry ingredients into the batter until just combined. Be careful not to deflate the batter.
Take a small portion of the batter and mix it into the melted butter in a separate bowl. Stir until smooth, then pour this butter mixture back into the main batter. Gently fold until fully incorporated.
Pour the batter into the prepared baking pan and smooth the surface.
Tap the pan gently on the counter a few times to release any trapped air bubbles.
Bake in a preheated 356°F (180°C) oven for 10 minutes, then remove the pan briefly and sprinkle chopped nuts evenly over the top. Return to the oven and continue baking for another 10 minutes, or until the top is set and lightly browned.
Remove the cake from the oven and let it cool completely in the pan or on a wire rack. Once cooled, cut into squares and enjoy.
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Notes
Palm sugar makes a difference - You can mix palm sugar with regular sugar if you prefer a lighter flavor, but using 100% palm sugar gives the best result. Its deep caramel notes blend beautifully with the spekkoek spices and give Ontbijtkoek its signature warm aroma.
Chop the nuts finely - Whether you’re using kenari nuts or pine nuts, chop them into small pieces. Larger chunks tend to sink to the bottom, while finely chopped nuts stay evenly distributed and give a nicer texture in every bite.
Temper the butter before adding it in - Always mix the melted butter with a small portion of the batter in a separate bowl first, then pour it back into the main bowl. This helps the butter blend smoothly without deflating the batter or causing it to separate.
Fold gently and efficiently - Once the dry ingredients are added, fold quickly but gently. Overmixing will knock out the air you worked so hard to build, and that air is what keeps the cake light.