Sweet potato brownies with espresso topping

This sweet potato brownie recipe with espresso icing is featured in Dr Joanna McMillan's book - Brain Food. As well as being a delicious chocolate treat, cocoa is rich in antioxidants.

  • 1 hr 30 mins cooking
  • Makes 16 brownies
  • Print

Dr Joanna McMillan says:

These days, I've noticed there's a trend for everything cocoa to suddenly be called cacao. Technically though, cacao is the unfermented, fresh seed; once fermented, it becomes cocoa, although some argue the word cocoa came from a misspelling of cacao. Cocoa powder (pure, non-sweetened, that is) is a great source of polyphenols - an antioxidant that may help to protect cognitive function as we age.
BRAIN FOOD by Dr Joanna McMillan (Bauer Books) rrp: $35
Available at and all good bookstores.


  • 1 medium orange sweet potato (400g), peeled, chopped
  • 2 tablespoons ground linseeds (flaxmeal)
  • 180 grams (51/2oz) sugar-free dark chocolate (70% cocoa)
  • 1 cup (220g) firmly packed brown sugar
  • 2 teaspoons vanilla extract
  • 2 tablespoons cocoa powder
  • 1 cup (120g) almond meal
  • 1/4 teaspoon bicarbonate of soda (baking soda)
  • 2 tablespoons natural flaked almonds, roasted
Espresso icing
  • 2 teaspoons instant coffee granules
  • 60 grams (2oz) sugar-free dark chocolate (70% cocoa)
  • 1/3 cup (80ml) pure maple syrup
  • 1/3 cup (75g) firmly packed brown sugar
  • 2 teaspoons vanilla extract
  • 1/4 cup (25g) cocoa powder


  • 1
    Place sweet potato in a medium saucepan with enough cold water to cover; bring to the boil. Cook, covered, for 15 minutes or until soft. Drain; return to saucepan. Mash until smooth.
  • 2
    Meanwhile, preheat oven to 180°C/350°F. Lightly grease a deep 20cm (8in) square cake pan; line base with baking paper.
  • 3
    Combine ground linseeds and 1/2 cup (125ml) hot water in a small heatproof bowl. Stand for 10 minutes.
  • 4
    Chop chocolate coarsely. Place chocolate, sugar, vanilla, 1/4 cup (60ml) water and sifted cocoa in a large heatproof bowl over a saucepan of simmering water. Stir until melted and smooth. Remove from heat; stir in mashed sweet potato. Add linseed mixture, almond meal and soda; mix well.
  • 5
    Pour mixture into pan. Bake for 1 hour or until firm to the touch. Cool slightly in pan.
  • 6
    Make espresso icing: Dissolve coffee in 1 tablespoon boiling water. Chop chocolate. Place chocolate in a small saucepan with syrup, sugar, vanilla and coffee; cook, stirring, over low heat until melted and smooth. Remove from heat; stir in sifted cocoa.
  • 7
    Spread top of brownie with icing and scatter with flaked almonds; stand until set. Cut into 16 squares to serve; dust with a little extra cocoa if you like.


Brownie will keep, stored in an airtight container at room temperature, for up to 3 days or can be frozen for up to 3 months.

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