Heat oven to 350°F. Combine flour, museli, baking soda, and salt in a medium bowl and whisk to incorporate.

Combine shortening and brown sugar in the bowl of a stand mixer fitted with the paddle attachment. Beat on medium until fluffy, about 4 minutes.

Add the cookie butter, egg, and vanilla and beat to combine. Add the dry ingredients and beat on low until fully incorporated.

Scoop dough by the tablespoon and roll in granulated sugar. Place on top baking sheets lined with parchment or silpats, about 1-inch apart. Bake for 10-12 minutes or until still soft in the middle but crisp on the edges.