Line a large baking sheet with parchment paper or a silicone mat.

In a medium saucepan over medium heat, combine granulated sugar, salted butter, and whole milk. Stir frequently and heat until it simmers.

Once at a simmer, boil vigorously without stirring for 45 seconds.

Remove from heat and stir in creamy peanut butter and vanilla extract until smooth.

Fold in rice krispies and gluten-free oats until well combined.

Use a cookie scoop to drop rounded portions onto the baking sheet.

Let the cookies cool at room temperature for 30 minutes or until set.

Optional: melt chocolate chips, drizzle over cooled cookies, and sprinkle with coarse sea salt.