Buttery, chewy sugar cookies with a crinkly texture from cream of tartar and sweet, crunchy toffee bits for a delightful treat.

1 cup unsalted butter, softened

1 1/4 cups granulated sugar

1/2 cup light brown sugar

1 egg + 1 egg yolk

1 tbsp vanilla extract

2 1/2 cups all-purpose flour

1/2 tsp baking soda

1/2 tsp cream of tartar

1/2 tsp salt

3/4 cup toffee bits (like Heath bits or homemade)

Optional: Extra sugar for rolling (for a sparkly finish)

Optional: A sprinkle of flaky salt on top before baking

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Preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.
In a large bowl, cream together the softened butter and both sugars until light and fluffy, about 2–3 minutes.
Beat in the egg, egg yolk, and vanilla extract until smooth.
In a separate bowl, whisk together the flour, baking soda, cream of tartar, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Fold in the toffee bits.
Scoop the dough into 1.5 tablespoon-sized balls (or use a cookie scoop). Roll the dough balls in extra sugar if desired.
Place the balls 2 inches apart on the prepared baking sheet. Slightly flatten the tops with your fingers or the bottom of a glass.
Bake for 9–11 minutes, until the edges are set but the centers remain soft. The cookies will crinkle as they cool.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.

The cream of tartar gives the cookies their signature crinkly texture and chewiness.

Rolling dough in sugar before baking adds a sparkly finish and extra crunch but is optional.

A light sprinkle of flaky salt on top enhances the sweetness.

To make gluten-free, substitute all-purpose flour with a gluten-free blend containing xanthan gum.

Butter can be browned for a richer flavor.

Store cookies in an airtight container for up to 5 days or freeze for up to 3 months.