1 cup all-purpose flour
1 cup regular rolled oats (not instant)
¼ cup packed light brown sugar
½ cup unsalted butter, melted
¾ cup packed light brown sugar
½ cup pure maple syrup
2 large eggs
¼ cup unsalted butter, melted (warm but not hot is fine)
2 tsp white or cider vinegar
1 tsp pure vanilla extract
¼ tsp fine sea salt
1 cup raisins or pecan pieces (optional)
1. Preheat the oven to 350°F (180°C). Lightly grease and line the bottom and sides of an 8-inch (20 cm) square pan with parchment paper.
2. For the base, stir the flour, oats and brown sugar by hand in a large bowl. Add the melted butter and stir together until the mixture is rough and crumbly (like a fruit crisp topping).
3. Press into the bottom of the pan, bake for 12 minutes to set (it will not brown) and then let cool in the pan on a wire rack. Leave the oven on. While the base is cooling, prepare the topping.
1. For the topping, whisk the brown sugar, maple syrup and eggs together until combined. Whisk in the melted butter followed by the vinegar, vanilla and salt.
2. Sprinkle the raisins (or pecans) (if using) in an even layer over the bottom of the base and carefully pour the maple syrup mixture over-top (you can move the raisins or pecans around to realign them, if required).
3. Bake for 25 to 30 minutes, until the topping bubbles just around the edges and is set when the pan is gently jiggled. Let cool completely in the pan on a wire rack before cutting into squares.
Tips and Substitutions
To prevent the top fluid layer from seeping around the edges and underneath the base of your tart, press the crumbly base gently up into the edges of the pan, so there is a little lip before pouring. Resist packing the base in too firmly, otherwise it can shrink away from the edges after baking, creating a gap for the filling to leak underneath. This tip can also be applied to any square with a fluid filling, such as a lemon square.
You can store the squares in an airtight container for 3 days at room temperature or for 5 days in the fridge. They can be frozen, but will soften up after thawing. If you must freeze, pack them in a single layer in an airtight container for no more than 1 month to avoid moisture building up. Thaw overnight in the fridge before serving.
Source and Credits
Excerpted from Set for the Holidays with Anna Olson
Courtesy of Penguin Random House