Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper or silicone baking mats. Ensure butter is at room temperature.
Cream softened butter and sugar together on medium speed for 2-3 minutes until light and fluffy. Mix in vanilla extract.
Whisk flour and salt in a separate bowl, then gradually add to the butter mixture on low speed just until dough comes together. Do not overmix.
Lightly flour your work surface and rolling pin. Roll dough to about ¼ inch thickness and cut out circles with a round cookie cutter.
Place cookies on prepared baking sheets about 1 inch apart. Gather scraps, re-roll, and cut more cookies until all dough is used.
Bake for 10-12 minutes until edges are just starting to turn golden. Centers should still look slightly pale.
Let cookies cool on baking sheet for 5 minutes, then transfer to a wire cooling rack to cool completely before adding chocolate.
Melt 6 ounces of chocolate chips with coconut oil in a microwave-safe bowl in 30-second intervals, stirring between each, until smooth. Let cool slightly.
Dip the bottom of each cooled cookie into melted chocolate and spread evenly with an offset spatula or butter knife. Place chocolate-side up on parchment paper.
Let chocolate set at room temperature for 15-20 minutes, or refrigerate for 5-10 minutes to speed up the process.
Melt remaining 4 ounces of chocolate chips the same way. Transfer to a piping bag, plastic bag with corner snipped, or use a fork.
Drizzle thin parallel lines of chocolate across the top of each cookie, keeping your hand steady and spacing consistent.
Let chocolate stripes set completely before storing, about 30 minutes at room temperature.