240 g (2 cups) all-purpose flour
160 g (2 cups) old-fashioned (rolled) oats
270 g (1 1/2 cups) brown sugar
5 ml (1 teaspoon) baking powder
1 ml (1/4 teaspoon) salt
200 g (1 cup) butter, melted
600 g (21 ounces) Nutella
Preheat oven to 350°F(180°C).
Butter a 9-by-13-inch baking pan.
Whisk together the flour, old-fashioned oats, brown sugar, baking soda and salt.
Pour the melted butter and stir to incorporate the butter.
Set aside 1½ to 2 cups of the mixture, then turn the remaining dough into the buttered pan.
Gently press the dough over the bottom of the pan.
Pour the Nutella over the oatmeal crust, then scatter the remaining oatmeal mixture over the top.
Bake for 25 to 30 minutes, or until the topping is golden brown.
Transfer the baking pan to a rack and cool for about 1 hour.
Bon Appétit!