What is a Big Small beer? Well, we’ll need some backstory:
To make beer, brewers stew malted barley with hot water to extract color, flavor and sugar (sugar = yeast food) from the grain to make a syrup. They separate that sugary syrup from the grain, move it into another vessel, season the syrup with hops and then feed the seasoned syrup to yeast (and the yeast eats the sugar and converts it to alcohol, making the beer). It is very easy to make beer.
Nowadays, brewers just adjust the water to grain ratio for higher and lower alcohol content beers, like making a simple syrup with a 1 : 1 ratio of water to sugar and a simple syrup with a 1 : 2 ratio of water to sugar. The color of the syrup will be the same (sugar has no color once dissolved) but one syrup will be much more concentrated. Unlike simple syrup, the malted barley also has flavor and color. These will also be more or less concentrated depending on the water ratio.
In old English brewing practices, instead of adjust the grain to water ration per brew, they would use the same grain multiple times to make a weaker and weaker syrup (and so weaker and weaker beers), which would result in weaker and weaker beers. This is called partigyle brewing (it would be similar to using the same coffee grounds to make multiple pots of coffee; the first pot would obviously be the strongest and most concentrated in color and flavor, and the following pots would be weaker in color and flavor).
The first, strongest, most concentrated sugary syrup would be used to make a strong beer. A lot of sugar for the yeast to eat means more sugar gets converted to alcohol which results in a higher alcohol content beer. A specific style example of a strong beer that was made from the first syrup (or “runnings”) in England is a Barleywine. A Barleywine, in its most basic sense, is just a very strong pale* ale (very concentrated in color, flavor and alcohol). It uses a whole bunch of pale malt to make a very concentrated syrup that is then fed to ale yeast to produce alcohol, i.e. strong pale ale.
The second or even third, less concentrated syrup (less color, flavor, & sugar extracted) was used to make lower alcohol content beers, called small beers. A specific style example of a small beer would be an Ordinary Bitter. An Ordinary Bitter, in its most basic sense, is a very weak pale ale (low concentration of color, flavor and alcohol). It uses a much less concentrated syrup made with the same pale malt that is then fed to ale yeast, i.e. weak pale ale.
*keep in mind: pale, especially in those days, was used to describe anything from straw/golden to amber in color. While the color of the malt is the same, the color molecules that dissolve into the stronger syrup from the outside of the grain will be closer together, which could make the stronger beer appear darker than the weaker one.
You don’t find many brewing this way anymore for many reasons (consistency being high on the list)…however, it is whimsical and we at WISEACRE like to dabble in the whimsy on occasion. We used this method to make Frostee Goatee, using the second, weaker runnings from Frozen Toast, a wheatwine (same as a barleywine, it just has wheat in addition to malted barley in the grain recipe).
Partigyle Brewing in action:

1A: Brewers stew malted barley with hot water to extract color, flavor and sugar (sugar = yeast food) from the grain to make a syrup.
2A: They separate that sugary syrup from the grain and move it into another vessel
3A: The syrup has a high concentration of color, flavor and sugar.
4A: Season the syrup with hops.
5A: Feed seasoned syrup to yeast. The yeast eats the sugar and converts it to alcohol, making the beer.
6A: Results in a very intensely flavored and boozy beer.

1B: Go back to separated grain. There is still a lot of sugary syrup sticking to it. Add more water and start the process again. This will make a less concentrated syrup (in flavor, color and sugar).
2B: Separate sugary syrup from the grain.
3B: Syrup will have a lower concentration of color, flavor and sugar.
4B: Season with hops (if using different hops than in Beer A, the hop flavor will obviously be different).
5B: Feed seasoned syrup to yeast.Yeast eats sugar and converts to alcohol; with less sugar to convert to alcohol, not as much alcohol will be produced
6B: Results in a less intense beer with less alcohol.
Beer A and Beer B will exhibit similar malt flavor and color (will just be more intense in Beer A). Beer A and Beer B could have very different hop flavor, depending on the hops and amount used in each.
Our Frostee Goatee Big Small Beer (Beer B in this example) used a lot of experimental hops that were not put into Frozen Toast Wheatwine (Beer A in this example) that give it an interesting coconut, guava, and sandalwood aroma. With a less intense malt flavor and more intense hop flavor, Frostee Goatee Big Small Beer tastes quite different from Frozen Toast Wheatwine. Frostee Goatee Big Small Beer also clocked in it at a whopping 5.9% abv, as opposed to 3% abv like most small beers, so it is pretty big for a small beer. Hence: Big Small Beer.