Preheat the oven to 350 F.

Line two rimmed baking sheets with silicone baking mats or parchment paper.

Place pecan pieces on one of the baking trays, evenly spread out, and toast for 5-8 minutes, stirring occasionally, until they are golden and fragrant.

Allow the pecans to cool, and then chop.

In a medium sized mixing bowl, whisk the flour, cornstarch, salt, and baking powder.

In the bowl of a stand mixer, cream the butter, brown sugar and granulated sugar together for 3-5 minutes, until light and fluffy.

Add in the eggs and mix on medium speed into just incorporated.

Add the sourdough discard and vanilla extract and mix to fully combine.

Gradually mix in the flour mixture, being careful not to overman.

Scrape down the sides periodically to ensure all the flour has mixed into the dough, and then fold in the chopped toasted pecans.

Cover the bowl with plastic wrap and place in the fridge to chill for at least 1 hour or overnight.

Scoop 2 Tablespoons worth of dough at a time and roll into a ball.

Place the cookie balls 2" apart on the prepared cookie sheets, sprinkle with flaky sea salt and then bake for 12-14 minutes, until golden brown on the edges and just set on the top.

Allow the cookie to cool on the sheet for 10 minutes before moving to a wire rack to cool completely.