Step 1

Preheat the oven to 350˚F. Line a baking tray with parchment paper.

Step 2

Beat the butter using elctric hand beaters on high speed until it's light and fluffy, approximately 2-3 minutes.

Step 3

Add the sugar and continue to beat on high speed until the mixture is creamy and pale.

Step 4

Add the vanilla and egg yolk and mix on low speed until just combined.

Step 5

Add the flour and continue to mix on low speed until the flour is just mixed in.

Step 6

Divide the dough into 12 equal portions and roll each portion into a round ball. If the dough feels a little dry or like it's not rolling smoothly, hold the dough in your hand for a few seconds until it starts to warm up, then roll it immediately.

Step 7

Place each ball on the baking tray and use your thumb to make a small indentation in the top of each cookie.

Step 8

Place a 1/2 teaspoon of jam (no more!) into the centre of each cookie.

Step 9

Bake for 15-7 minutes until the cookies are lightly golden.

Step 10

Remove from the oven and place on wire cooling racks until the jam is cool (around 30 minutes - don't try to eat these right our of the oven as they will be very hot!).