The Knight of the Burning Pestle is only the second work I've read by Francis Beaumont and John Fletcher (the first being Philaster, composed a little later). It was first performed in 1607 and first published in 1613, making it one of their earlier collaborations. However: some do believe that Francis Beaumont wrote The Knight alone, others argue it was indeed with Fletcher. As my edition (Oxford World Press' Six Plays by Contemporaries of Shakespeare, 1915) states it is Fletcher and Beaumont, I shall go with that, though it must be stated that there is a good argument for saying it was Beaumont wrote it alone.
The play is a comedy that begins with the start of another play, 'The London Merchant':
Several Gentleman sitting on Stools upon the Stage. The Citizen, his Wife, and Rᴀʟᴘʜ sitting below among the Audience.
Enter the Speaker of the Prologue.
Sᴘᴇᴀᴋᴇʀ ᴏꜰ ᴛʜᴇ Pʀᴏʟᴏɢᴜᴇ: 'From all that's near the court, from all that's great,
Within the compass of the city-walls,
We now have brought our scene...'
Citizen leaps on the stage.
Cɪᴛɪᴢᴇɴ: Hold your peace, goodman boy!
Sᴘᴇᴀᴋᴇʀ ᴏꜰ ᴛʜᴇ Pʀᴏʟᴏɢᴜᴇ: What do you mean, sir?
Cɪᴛɪᴢᴇɴ: That you have no good meaning: this seven years there hath been plays at this house, I have observed it, you have still girds at citizens; and now you call your play 'The London Merchant'. Down with your title, boy! down with your title!
Sᴘᴇᴀᴋᴇʀ ᴏꜰ ᴛʜᴇ Pʀᴏʟᴏɢᴜᴇ: Are you a member of the noble city?
Cɪᴛɪᴢᴇɴ: I am.
Sᴘᴇᴀᴋᴇʀ ᴏꜰ ᴛʜᴇ Pʀᴏʟᴏɢᴜᴇ: And a freeman?
Cɪᴛɪᴢᴇɴ: Yea, and a grocer.
The exchange goes on and the Citizen and Wife remain on stage throughout, certain that if they did not the players of 'The London merchant' would misrepresent them. And so the wife and Citizen act almost as directors or censors, and they demand a new character for the play: the Knight of the Burning Pestle, which will be played by Ralph, the Citizen's apprentice; he has demonstrated his skills by speaking some lines from Shakespeare's Henry IV Part I:
'By Heavens, methinks, it were an easy leap,The actual quote, from Hotspur, is from Act I.iii:
To pluck bright the honour from the pale-faced moon;
Or dive into the bottom of the sea,
Where never fathom-line touched any ground,
And pluck up drowned honour from the lake of hell.'
By heaven, methinks it were an easy leap
To pluck bright honour from the pale-fac'd moon,
Or dive into the bottom of the deep,
Where fadom line could never touch the ground,
And pluck up drowned honour by the locks,
So he that doth redeem her thence might wear
Without corrival all her dignities;
But out upon this half-fac'd fellowship!
No matter, as I say he gets the part and from here we descend into farce. Ralph, the "Grocer Errant" (i.e. knight-errant, or wandering knight) causes chaos for the players of 'The London Merchant' (the plot of which is similar to Dekker's The Shoemaker's Holiday, 1599) and so The Knight of the Burning Pestle, or 'The London Merchant' effectively has two strands and becomes a play within a play: a pretty early example of meta-fiction, in short. Ralph bumbles his way though as the Citizen and his Wife shout at the players; things get complicated, then surreal, but above all else it is very amusing. It is, essentially, a play about the audience and how an audience may interpret a play, understand or misunderstand, and how the actors and director attempt to appeal not only to their conventional audience but also maintain some free reign to be creative. It's a fun and unusual read, but I suspect it would be much better to watch than to read.