How to throttle power consumption of a heating coil?
The argument:

If your heating element is rated to dissipate 2300 watts with 230 volts across it, then when it's dissipating 2300 watts the current through it will be:

I = P/E = 2300W/230V = 10 amperes,

and its resistance will be:

R = E/I = 230V/10A = 23 ohms.

In order for the element to dissipate 1400 watts, then, the voltage across it must be decreased to:

E = sqrt (PR) = sqrt (1400W * 23R) ~ 180 volts,

and the current through it decreased to:

I = P/E = 1400W/180V ~ 7.8 amperes 

Since the mains voltage is unchangeable at 230 volts, then in order to limit the current through the heating element to 7.8 amperes, a series attenuating element must be introduced into the circuit which will drop the mains' 230 volts down to the 180 volts required by the heater.

That's 50 volts, and it must pass the 7.8 ampere heater current, so its resistance will be:

R = E/I = 50V/7.8A = 6.4 ohms.

The total resistance of the series string will therefore be 29.4 ohms, the sum of the two resistances,.

If we use a capacitor to losslessly drop the voltage to the heater, then we can define the resistance of the string as an impedance,

Z² = R² + Xc², where:

Z is the impedance of the string,
R is the heater resistance, and
Xc is the reactance of the series capacitor, all in ohms.

Rearranging to solve for Xc we get:

Xc = sqrt (Z² - R²) = sqrt (864.4R - 529R) = 18.3 ohms

and, finally, to get the capacitance,

C = 1/(2pi f Xc) = 1/(6.28 * 50Hz * 18.3R )= 174 microfarads .

Cornell-Dubilier makes a nice line of caps which seem perfect for this application.

Pricey, no doubt, but probably less so - and certainly lighter and smaller - than an inductor or a transformer capable of doing the same job.

The LTspice proof:

Version 4
SHEET 1 1460 680
WIRE 256 64 96 64
WIRE 256 96 256 64
WIRE 96 160 96 64
WIRE 256 192 256 160
WIRE 96 320 96 240
WIRE 256 320 256 272
WIRE 256 320 96 320
WIRE 96 368 96 320
FLAG 96 368 0
SYMBOL voltage 96 144 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value SINE(0 325 50)
SYMBOL cap 240 96 R0
SYMATTR InstName C1
SYMATTR Value 180µ
SYMBOL res 240 176 R0
SYMATTR InstName R1
SYMATTR Value 23
TEXT 104 344 Left 2 !.tran 1