in a heavy-bottomed saucepan, warm the milk over medium heat, stirring occasionally. You just want it to be warm about 110°F.
In a separate heavy-bottomed saucepan, melt the butter over medium heat until it has melted. Whisk the flour into the melted butter a little bit at a time, until it is fully incorporated into the butter, giving you a paste. This is called a roux. Heat the roux for another minute or so to cook the flour.
Add the warm milk to the roux very slowly while whisking. Whisk vigorously to break up any lumps. Reduce the heat to simmer and simmer until the sauce thickens.
Add salt and shredded cheddar. Stir until smooth.
QUINOA
Meanwhile, cook the quinoa according to package directions. When cooked, mix quinoa with cheese sauce, stirring until combined. Taste and adjust salt. Add pepper if you like.