Prepare cheesecake filling by beating cream cheese with sugar and vanilla until fluffy, about 3-5 minutes. Freeze in 18 equal discs for at least 30 minutes.

Make strawberry jam by cooking diced strawberries and sugar for about 45 minutes until thickened. Cool completely.

Mix cookie dough by whisking flour, baking powder, baking soda, and salt in one bowl. Cream butter and sugar in another, then add egg and vanilla.

Layer the jam into the dough by folding it gently to create a marbled effect.

Form cookies by encasing frozen cheesecake discs in dough and rolling in sugar. Place on a baking sheet.

Bake cookies at 350°F (175°C) for 11-12 minutes and let cool for 10 minutes before transferring to a wire rack.