What ingredients produce the nutty flavor in a nut brown ale?

I guess it really depends on the type of nut brown ale you are brewing. I mean if it is a peanut brown ale I would reach for more peanuts and if it is a hazelnut brown ale I would add more hazelnuts. Sorry, but I couldn’t resist the obvious! The nutty flavors found in brown ales and other dark beers come from malt. And nutty flavors in malt are formed during kilning when reducing sugars react (glucose and maltose, for example) with amino acids and polypeptides in the frequently cited Maillard reaction, named after the French chemist Louis Camille Maillard who discovered the reaction in 1912. Although pale malts do contain Maillard reaction products (MRPs), it is the group of MRPs that undergo Strecker degradation, a reaction where intermediates in the Maillard reaction combine with amino acids and condense into nitrogen-containing cyclic molecules. These molecules have biscuity, nutty and toasty aromas. Adolph Strecker (1822–1871), by the way, was a German chemist born in Darmstadt who developed a method to synthesize amino acids and identified the so-called Strecker degradation in the laboratory before the Maillard reaction was discovered. The products of the Maillard reaction and Strecker degradation range from toasty to burnt — in the middle is nutty. Maltsters can adjust kiln temperature and moisture content during kilning and roast malts with varying degrees of modification to influence the flavors of roasted malts and ultimately beer flavor. One of my favorite brews is a brown ale that my brewery makes once every year or so that contains brown malt. The signature flavor from the brown malt is a dry, roasty nuttiness that I really like. Other malts that give the type of flavor you seek include Munich malts, especially darker types, biscuit malt, aromatic malt, amber malt and other high-kilned malts. One of the best ways to select malt for a brew is to taste it or, as many brewers say, “chew” the malt. Munching on malt is a great way to evaluate its character as it gives a good idea of hardness or friability (ease of milling), can sometimes indicate evenness of modification and gives a straight-up sensory profile of that one malt. Sometimes when I am searching for a flavor I can’t adequately describe with words I find what I am after when chewing on malt samples.