Preheat your oven to 350F (175C). Line a cookie sheet with parchment paper and pour flour evenly over the parchment. Once oven has preheated, transfer flour to center rack and bake for 7 minutes (flour temperature should exceed 165F to eliminate risk of E.coli).
Remove flour from oven and allow to cool completely.
Meanwhile, cream together butter and sugars using an electric mixer or stand mixer. Beat until creamy and well-combined. Scrape the sides of the bowl and beat on high speed for one minute.
Add condensed milk, vanilla extract, and salt. Stir until combined, scrape the sides of the bowl again, and gradually increase speed to medium-high and beat another 1-3 minutes.
Once flour has cooled, measure out ¼ cup (30g) and set aside. Gradually stir remaining 2 cups (250g) into butter/sugar mixture until combined. If texture isn't firm enough to roll, add remaining flour from the reserved ¼ cup, 1 Tablespoon at a time, but only as much as is needed. Discard any extra/unneeded flour.
Stir in mini chocolate chips.
Scoop cookie dough by 2-teaspoon-sized scoops and roll between your palms to form a smooth ball. If the dough is too greasy you can add additional flour, or I recommend waiting 10 minutes or even refrigerating the dough for 10 minutes. Since the butter is warm from being beaten so much the dough will seem softer than it really is, allowing it to sit for 10 minutes or so usually helps to firm up the dough and make it easy to roll.