Line 2 baking sheets with parchment paper and set aside.
In a medium size saucepan over medium-high heat, combine the butter, sugar, brown sugar, and milk. Whisk continuously until the butter has fully melted and then continue to whisk occasionally while brining the mixture to a boil.
1/4 cup salted butter, 1 cup sugar, 1/2 cup brown sugar, 1/2 cup milk
Once boiling, allow mixture to continue boiling for another minute or so, then remove from heat and stir in the Biscoff Cookie Butter and vanilla extract. Mix well, until thoroughly combined.
2/3 cup Biscoff Cookie Butter, 1 TBS vanilla extract
Fold in the oats, then allow the mixture to sit for 5 minutes or so to thicken.
3 cups rolled oats
Then, using a 2 tablespoon cookie scoop, scoop cookies onto a lined baking sheet. Gently flatten the tops cookies by pressing down with the back side of a spoon (optional).
Place cookies in the refrigerator for about an hour to harden. These cookies tend to be pretty sticky, so a longer chill time is better.
Store leftover cookies in an airtight container in the refrigerator for up to 1 week or freeze for up to 3 months.
Notes
*Using quick-cooking oats will yield a smoother, less chunky cookie.