1-Preheat your oven to 350°F and line a baking sheet with parchment paper. Place 4-inch tart tins on the sheet, spacing them out, and spray them with non-stick spray if you like. In a bowl, beat the softened salted butter and granulated sugar until they’re well combined, then add the large eggs and beat until creamy.

2-Mix in the canola or vegetable oil and vanilla extract, beating until the mixture is light and fluffy. In another bowl, combine the all-purpose flour, cornstarch, baking powder, and salt. Gradually add these dry ingredients to the wet mixture on low speed until everything is just combined.

3-Shaping and Baking the Cookies: Scoop ¼ cup of dough into each tart tin and press it down to form a well in the center, making sure there are no holes at the bottom. Chill the tins in the fridge for 15 minutes to help the dough hold its shape. Once chilled, bake for 12-15 minutes until the edges turn golden, then gently tap the tins to flatten any puffed centers and let them cool in the tins before moving to a rack.

4-For the pastry cream, whisk together granulated sugar, whole milk, heavy cream, egg yolks, cornstarch, and salt in a saucepan. Heat over medium while stirring until it simmers and thickens, then boil for 30-60 seconds. Strain if needed, add salted butter and vanilla extract, whisk until smooth, cover with plastic wrap touching the surface, and chill until cool.

5-To make the ganache, heat heavy cream until it simmers, pour it over semisweet chocolate chips, and let it sit for 1-2 minutes. Whisk until smooth, stir in salted butter, and let it cool for 5-10 minutes so it’s pourable. Finally, spoon the pastry cream into the cooled cookie wells, spread it out, drizzle the ganache on top, and chill the cookies for 1-2 hours before serving.