In a large mixing bowl, whisk together the flour, baking soda and salt. Set aside.
2 1/4 cups (281 grams) flour, 1/2 teaspoon baking soda, 1/2 teaspoon salt
In another large mixing bowl with an electric hand mixer, beat together the butter, oil and granulated sugar until well blended.
1/2 cup (113 grams) unsalted butter, 1/2 cup (102 grams) vegetable oil, 1/2 cup (100 grams) granulated sugar
Add the egg and vanilla extract and beat until fully incorporated.
1 large egg, 1 teaspoon vanilla extract
Gradually beat in the dry mixture to the wet mixture, mixing just until combined. Be careful not to overmix. The dough can be wrapped in plastic wrap, placed in a Ziploc, and refrigerated for up to 3 days.
Grease 24 cavities of two standard muffin pans.
Roll the dough into twenty-four 27-gram balls. Place one in the center of one of the cavities and squish down to create a little crust that you’re going to fill. You don't need to create a thin pie crust kind of shell.
Chill for 30 minutes or freeze for 15. Meanwhile, preheat the oven to 375 °F (190 °C) and place a baking sheet large enough for your muffin pans in the lower third section of your oven.
Place the cold muffin pans on the preheated baking sheet and bake for 12 minutes or until nicely browned. The bottom won’t brown as nicely as the sides, but that’s normal.
Remove from the oven, press them down with your fingers or a spoon to make a more defined indentation where the filling will go.
Let cool for at least 15 minutes on a cooling rack while you prepare the filling and lower the temp to 350 °F (175 °C).