It was from a paragraph in Inventing the Future by Srnicek and Williams. And I slightly misremembered. It wasn't the wall, it was the entire blockade that kicked off the Cold War:

Following World War II, the ordoliberals began to move into government positions and implement their ideas, establishing the material and institutional foothold from which to shape economic ideology. The first, and perhaps most historically significant position, was the appointment of Ludwig Erhard to the directorate of economics in the postwar administrative zone of the British and US militaries. With the support of a fellow ordoliberal, Wilhelm Röpke, Erhard simultaneously eliminated all existing price and wage controls, and drastically cut income and capital taxes. This was a radical deregulatory move, and one that compelled the Soviet Union to establish a blockade on Berlin and inaugurate the Cold War.[33] In the decades that followed, ordoliberals would come increasingly to populate significant positions in the German Ministry of Economics, with Erhard himself becoming Chancellor in 1963. But despite their intentions, the ordoliberals lacked a principled distinction between legitimate and illegitimate government interventions – an ambiguity which facilitated the German economy’s transformation into increasingly Keynesian forms. Interventions to maintain competition shaded into interventions to provide welfare, and by the 1970s Germany had become a standard social democratic state. The difficulties encountered in the policy world did not stop neoliberalism from innovating on other terrains, though – in particular, the space of the so-called ‘second-hand dealers’ in ideas.

The source 33 they cite is: Peck, Constructions of Neoliberal Reason, p. 57. Here is the relevant information from that:

Erhard’s actions were bold, to say the least. He was legally forbidden to modify the system of price controls without the explicit approval of the Allied authorities, but the regulations said nothing about the outright abolition of the entire regulatory regime. It was through this loophole that Erhard leapt, causing the Allied Commander, General Clay, to fume: “Herr Erhard, my advisors tell me that what you have done is a terrible mistake,” to which Erhard famously replied, “Herr General, pay no attention to them! My own advisers tell me the same thing.”84 To the contrary, of course, Erhard’s Mont Pelerinian mentor, Wilhelm Ro¨pke, not only supported the plan, he was, in effect, its joint architect. By any measure, this was a decisive moment. Three days later, the Russians established the Berlin blockade, in order to contain the effects of the currency reform, triggering the beginning of the Cold War.85 Erhard’s bold intervention has been authoritatively evaluated as the “most fateful event in the history of postwar Germany.”86

Eventually Erhard had to eat shit and move back to a socdem approach (his Wikipedia page has info on this and his connections to Mont Pelerin).