Place 1 cup of sliced strawberries and ¼ cup of granulated sugar in a small saucepan. Use a masher or fork to break down the strawberries into a pulp.

Then heat the mixture over medium-low heat for a couple of minutes while stirring frequently.

In a small bowl, combine 2 tablespoon water and 1 tablespoon cornstarch to make a cornstarch slurry. Pour into the strawberry mixture and continue to cook it until it becomes thick like jam. This usually takes about 5 min.

Pour the mixture into a bowl and place in the fridge uncovered to cool.

Preheat the oven to 350 F / 175 C and line two large baking sheets with silicone baking mats or parchment paper. Set aside.

In a large bowl or the bowl of a stand mixer, beat 1 cup butter and 1 cup granulated sugar and mix on a medium-high speed for a couple of minutes, until the mixture becomes lighter in color.

Then mix in 3 tablespoon of strawberry reduction, 1 large egg + 1 large egg yolk, 1 teaspoon vanilla extract, and a small drop of red gel food coloring (optional) on a medium speed until fully incorporated.

Add 2 ½ cups flour, 2 teaspoon baking powder, and 1 teaspoon fine salt, and mix on low speed until it is JUST incorporated.

To add the strawberry reduction to the dough, scoop 2 tablespoon of strawberry reduction to the top of the dough, then use a butter knife to gently marble the jam into the top of the dough.

Add ¼ cup of granulated sugar to a shallow dish. Use a 3-tbsp cookie scoop to scoop the dough into balls, then roll them in sugar until they're evenly coated.

Place the cookies about 3 inches apart on the prepared baking sheets.

Bake for 10-12 minutes, or until the edges of the cookies are set but the centers are still a bit soft.

Cool for 15 minutes on the pan, then move the cookies to a wire rack to finish cooling.

If you marbled the strawberry reduction into the dough, it can end up caramelizing at the edges of the cookies and stick to the parchment paper. Gently use a flat spatula to separate any sticky bits without breaking the cookies.

If desired, spread any remaining strawberry reduction on top of the cookies right before eating.