As sharp as mustard is a simile.  Sharp in this context usually means quick-witted, but mustard is a condiment with a sharp taste.

Bakewell tart is named after a town in Derbyshire.  It consists of a pastry flan case, a layer of jam and a filling which includes ground almonds.

Eccles cakes are named after a town in Greater Manchester.  They are more of a pastry than a cake, not unlike Banbury cakes, which are pastry filled with dried fruit.  Banbury is a town in Oxfordshire made famous by a nursery rhyme mentioned in an earlier post.

Two Banbury cakes Photo credit Redrose64 via Wikipedia
http://en.wikipedia.org/wiki/File:Banbury_cake.jpg

Pontefract cakes are a different sort of confectionery altogether, being liquorice medallions.  One of my pet hates is the mispronunciation of the word liquorice.  The ending should rhyme with hiss.  Many people say it as liquorish, which is a completely different word,  meaning tipsy or drunkPontefract is a town in Yorkshire.

Liquorice allsorts are a popular selection of sweets.  (People in the North of England seem to call all sweets “toffee” and US English uses “candy”.)

Faint from lack of nourishment is a cliché.  I don’t know about you, but I start to go light headed if I am physically active and wait longer than usual between meals.

A silly sausage is sometimes a term of endearment. 

A sausage machine churns out items which are more or less identical.

Bangers and mash is an expression meaning sausages and mashed potato.  If sausage skins are not pricked, the sausage may burst with a loud report.  The sausages I cook these days do not need to be pricked.  I wonder what the skins are made of!

Living high on the hog means eating rich food.  A hog is a pig.  Hog-roasts have become very popular for outdoor parties.

Below the salt was where the less important people were seated at a long table in the olden days.

Pot luck is what visitors are given to eat when they arrive at short notice.  I imagine the derivation is whatever happens to be in the cooking pot at the time.

A friendship cake is a cake mixture containing yeast.  I have no idea where these begin, but sometimes there is one on offer.  The instructions describe how much flour (and other ingredients) to add.  The mixture grows, some is baked and some given away with the instructions. 

A rotten apple is no use and can spoil others stored with it.

A good egg is a reliable person and a rotten egg smells terrible!

To egg someone on is to urge them to do something.  There is no connection with eggs here.  The Dictionary of Modern Phrase gives the derivation as being a corruption of the Old Norse eggja, an edge and the definition, “edge someone further into action”.  I have known it used in cases where the action encouraged was good or bad.

Most people benefit from encouragement.  The writer to the Hebrews (3:12-13) (NIV) recommended a daily dose of encouragement.

See to it, brothers, that none of you has a sinful, unbelieving heart that turns away from the living God.  But encourage one another daily, as long as it is called Today, so that none of you may be hardened by sin’s deceitfulness.