Cream the butter and sugar together until light and fluffy
Add the flour and beat until dough-like clumps start to form
Tip the mixture out onto a floured work surface and use your hands to gently knead it together into a smooth ball of dough - this shouldn't take long, only 30 seconds or less
Use a large rolling pin to roll the dough out to ¼ inch thick, use cookie cutters to cut out circles, and use a small heart cookie cutter to cut out the center of half of the circles. Transfer them to the prepared cookie sheet
Chill the cut-out cookies for 30 minutes
When the chill time is almost up, preheat the oven to 325°F / 160°C
Bake the cookies for 13-16 minutes, bake time will vary according to thickness so it's best to look for visual cues when they are ready. As soon as the very edge of any of the cookies starts to turn golden brown, remove them from the oven. They should still look very pale in the middle
Leave the cookies on the pan for 5 minutes, then transfer to a wire rack to cool
Once completely cool, spread about a teaspoon of strawberry jam onto the bottom cookies and gently press the top cookies on top. (It helps if your jam is at room temperature so it will spread more easily)
Notes
Make sure to chill the dough for at least 30 minutes before baking - this will ensure the cookies don't spread in the oven and hold their shape perfectly. You can use any jam you like in the middle - homemade or storebought. You can also fill these cookies with other fillings - see blog post above for some inspiration.