1 Preheat the oven to 180 degrees or 160 degrees if using a fan oven. Grease and line two baking trays if you have them, otherwise you'll have to bake the cookies in two batches.

2 Put the butter and peanut butter into a stand mixer fitted with a beater attachment and cream together until soft and smooth. Add the brown sugar and the caster sugar, and continue to beat until well combined.

3 Add the egg, and mix well. Sieve in the self-raising flour with the salt, and beat until the dough comes together.

4 Divide the mix into 24, (about 30g each if you want to weigh them to be exact), and roll into balls. Place the cookie balls onto the greased and lined baking trays, leaving a two-inch gap between each. If you don't have two baking trays, bake the cookies in two batches.

5 Using a flat drinking glass, dip the base of the glass in a little flour and press onto each ball to flatten slightly. The flour will stop the dough from sticking to the glass.

6 Bake the cookies in the preheated oven for about 12 minutes. The cookies will have spread out slightly and have a darker browned edge, but a paler golden centre. Allow the cookies to cool a little before transferring to a wire rack to cool completely.

7 For the filling: Put the butter and peanut butter into a stand mixer fitted with a beater attachment. Cream together until soft and smooth. Add the icing sugar and the salt, and continue to mix until completely combined. Add a splash of milk if the buttercream needs to be loosened a little. Set aside until ready to serve.

8 To assemble: Spread or pipe one or two tablespoons of peanut butter buttercream onto 12 of the cookies, and spoon a teaspoon of jam on top. Sandwich together with a second cookie. The finished cookie sandwiches can be stored in a sealed container for up to three days.