In a large mixing bowl, using either electric hand beaters or a stand mixer with the paddle attached, add softened butter.
Beat butter for a few seconds to break it up and it begins to turn creamy. This makes it easier on your beater when the sugar is added.
Add sugar and vanilla. Beat on high for 2 minutes until mixture turns light/pale and creamy. Scraping down the sides as needed.
Add egg and beat for 15 seconds until well combined. Scrape down the sides of the bowl again.
Sift over flour and baking powder.
Beat until a soft dough forms, about 20 seconds. Scraping down the sides as needed.
Bring the dough together into a ball/disc using your hands or a spatula.
Transfer bowl with dough inside to the refrigerator to chill for 30 minutes. TIP: if your bowl is too large for your fridge, wrap the dough in plastic wrap and place in the fridge without the bowl.
Preheat oven to 180ºC fan-forced (356ºF fan-forced). Line a large baking tray/sheet with parchment paper, set aside.
Pick up two teaspoons worth of dough weighing about 15g each (0.5oz) and roll into a smooth ball. Place on lined sheet.
Slightly flatten the dough ball into a disc using your palm or fingers (refer to process images above in post).
Create the indent by pressing your index finger joint into the disc (refer to process images above in post for a visual). You can use your thumb to create the indent or the handle of a wooden spoon.
Repeat above process with remaining dough, creating the indents as soon as you flatten each into a disc as it will help prevent the dough from cracking.
Fill each indent with strawberry jam.
Bake for 10-12 minutes until very lightly golden around the edges. The majority of the cookie will still be pale.
Remove from oven and allow to cool on pan for 5 minutes.
Carefully transfer cookies to a wire rack to cool completely.
Serve and enjoy!