If baking the cookie layer: Preheat oven to 350°F (175°C). Line a 9x9-inch pan with parchment, leaving overhang.

Cream butter with brown and white sugars until fluffy. Beat in egg and vanilla.

Whisk flour, oats, baking soda, cinnamon, and salt. Stir into wet ingredients until combined. Press the dough evenly into the pan.

Bake 12–15 minutes, until edges are set and the center is soft but not wet. Cool completely. This will be your base for bars or crumbled into parfaits.

For the cream filling: In a clean bowl, beat cream cheese until smooth. Add powdered sugar, vanilla, and salt; mix until creamy.

In a separate bowl, whip the heavy cream to medium peaks. Gently fold the whipped cream into the cream cheese mixture until light and fluffy.

To make Oatmeal Cream Pie Bars (scratch or shortcut): Scratch: Spread the cream filling over the cooled oatmeal cookie base. Chill 2–3 hours, then slice into bars.

Shortcut: Line a pan with store-bought oatmeal cream pies, pressed side-by-side. Spread cream filling on top, chill, and slice.

To make Parfaits: Crumble baked cookie layer or chop store-bought pies. Layer crumbs, cream, and toppings (caramel, nuts, chocolate chips) in small glasses. Chill 30–60 minutes.

To make Sandwiches: Bake smaller oatmeal cookies. Pipe cream filling between two cookies. Chill 30 minutes for neater edges.

Finish with a drizzle of caramel or a dusting of cinnamon. Serve cold for the best texture.