Preheat the oven to 350°F. Lightly grease an 8-inch-square brownie pan.

Melt the chocolate chips and coconut oil together. You can do this two ways: Microwave method: combine them in a microwave-safe bowl and heat in 30-second intervals, stirring between each one, until smooth. It usually takes about 90 seconds total. Stovetop method: set a heatproof bowl over a pot of gently simmering water (don't let the bowl touch the water) and stir until everything is melted and combined. Either way, don't rush it, keep it low and slow, mixing with a rubber spatula and removing from the heat even before all the chocolate melts. It will continue to melt off the heat.

Pour the melted chocolate mixture into a large mixing bowl and let cool to room temperature; this should take about 10 minutes. In the meantime, measure everything else out.

Beat the sugar, applesauce, and cornstarch into the melted chocolate. Mix until very smooth. Stir in the vanilla.

Mix in half the flour, the baking powder, cocoa powder, and salt. Fold in the walnuts, then add the remaining flour and mix until no dry clumps are left.

Transfer the batter to the prepared pan and use a spatula to spread it out evenly. Bake for 18 to 20 minutes, until the edges are lightly pulling away from the pan. Place the pan on a cooling rack and slice the brownies when cool.

They are especially wonderful warmed up with a scoop of ice cream!