1. Remove the cream layer inside the oreo cookies. Crush the cookies. Set aside.
2. Cut a piece of parchment paper to cover the bottom and sides of a 26x30cm jelly-roll pan.
3. Sift flour, cocoa and coffee powder into a medium bowl and set aside. Pre-heat the oven to 190C degree.
4. Beat the eggs and sugar with an electric hand mixer in another medium bowl, using a hot bath until it gets creamy.
5. Add the sifted flour mixture and mix gently using spatula until smooth.
6. In a small cup, add butter and milk and microwave it for 15sec at 600W. Gently mix until completely melted. Then add into the mixture gently. Mix well to combine.
7. Pour the batter into the prepared sheet pan, flatten the surface with a spatula. Tap gently the bottom of the pan to punch out the air.
8. Bake for about 12 minutes or until a cake tester inserted in the middle comes out clean.
9. Remove from the oven, immediately loosen the edges of the cake from the pan gently. Flip the cake upside down. Peel off the parchment paper from the cake (I even use A4 paper sheets sometimes!). Cover the cake and let it cool down completely.
10. Combine sugar and heavy cream in a bowl and whip until firm-peak. Add crushed oreo and mix.
NOTE : if your cream is less than 35% fat, I recommend you to add whipped cream stabilizer (I used "cremfix" here). In that case, mix cream stabilizer to the sugar ahead of this step. Add when your cream is getting a soft peak, then continue to beat until firm-peak.
11. Spread the whipped cream from #10. Spread more thinly along the front edge of the cake (the part that will be rolled last).
12. Roll the cake together with the parchment paper and then tighten the paper to firm it up. Wrap the paper firmly around the cake. Refrigerate a few hours to set.