Step 1

Smash the digestive biscuits to a fine crumb.

Step 2

Tip them into your square, loose-bottomed, 25cm/10 inch straight-sided tin.

Step 3

Add the melted butter and mix until combined.

Step 4

Press down firmly to create an even base, then place in the fridge to chill.

Step 5

In a bowl, whisk the cream cheese, yogurt and vanilla until thick.

Step 6

Add the sugar and whisk again.

Step 7

Tip the filling into the tin. Level off and return the tin to the fridge.

Step 8

Place the lemon juice, lemon rind, butter and sugar into a bowl and heat gently over a pan of simmering water until the butter has melted.

Step 9

Add the room temperature eggs and whisk until fully combined.

Step 10

Continue to heat over the pan, stirring occasionally until it has thickened enough to leave a trail if you run your finger over the back of the spoon.

Step 11

Leave to cool completely. It will thicken further.

Step 12

Spoon the curd into the tin, level off and return to the fridge to firm up overnight.

Step 13

Cut into bars to serve.