Mocha Viennese fingers

Since my son has been living with us, my cake and biscuit tins are permanently empty! What to make next? This month's added ingredient from We Should Cocoa's monthly challenge is coffee so I decided to make some Viennese fingers with a coffee cream filling. They will also be my contribution to the monthly Alpha Bakes challenge, but more of that later on. 
The June We Should Cocoa challenge is guest hosted by  The Kitchen Maid and the usual hosts of this monthly challenge are Choclette and Chele. These are the rules.

Makes 12

150g butter
75g icing sugar, sifted
150g plain flour, sifted
100g dark chocolate
3 tspn instant coffee
1 tspn boiling water

filling:

Preheat oven 190C/gas5
Grease two baking sheets and line with baking parchment.

Beat 100g of the butter with 25g of the icing sugar, then work in the flour. Put in a piping bag with a large star nozzle and pipe twelve 5cm long strips onto each baking sheet. I find it easier to stand the piping bag in a jug and turn the top over the sides of the jug, then fill with the mixture.
Bake for 10-15 minutes until a pale golden brown. Transfer to a wire rack to cool.
Melt the chocolate in a bowl over a pan of hot water or in the microwave. Dissolve the coffee in the boiling water. Beat together the remaining butter and icing sugar with the coffee. Sandwich the biscuits together in pairs with the coffee buttercream, then dip one end of each in melted chocolate. When hardened, dip the other ends in the chocolate. Keep for about a week in an airtight tin.

There are so many different recipes for these fingers, some using cornflour. They have a lovely melt in the mouth texture, and the coffee filling goes well with the chocolate. I know that I said in my last post that I don't like buttercream filling, but the others do, and it is easier to make!

I'm going to also use this post as my contribution to the Alpha Bakes monthly challenge. This is hosted alternately by Ros and Caroline and you can find the rules here. Ros is the June host and the randomly chosen letter is V, so my Viennese fingers fit in nicely.