My idea is to print a small box containing the electronics that can sit next to the oven, just like a 3D Printer setup. When not in use, the wires between the control box and the oven get disconnected and the box can be hopefully stored INSIDE the oven.

In order to start making this, I started rummaging through my basement. 

Here's what I found (that was relevant to this project):

• One Kenmore 110V 1000W toaster oven -> This oven is less than ideal for this because it has resistive elements.  On the upside, it's basically free since I didn't use it in over a decade.
• Arduino 2560 -> Good for this project - lots of memory.
• TinyRTC sporting a DS1307 w/ AT24C32 EEPROM.
• 4x20 LCD display.
• I2C to LCD piggyback adapter -> This is a really useful piece of equipment.
• MAX6675 w/ thermocouple -> Cables are steel-braided and good to 600C.
• SD Card Reader -> Full size SD - quite an old one.
• Grayhill 62P series quadrature encoder. This is great for an input - just like a 3D printer. Unfortunately it does not have a feature for pressing a push-button so I will have to implement that separately.
• One button for OK.
• One piezo-beeper for user notifications.
• I took apart an old power adapter to use as the power supply for the Arduino. 110VAC to 12VDC.
• Several MOC3043s and some MAC12DG triacs. I have a serious disdain for relays so I'm avoiding them as usual.
• A square 80mmx25mm 12V fan for cooling the heatsink for the triacs.

A quick brainstorming session yielded the below preliminary schematic.