Chicken Thighs with Lemon Sauce - Cooking like a Boss

Recipe from https://recipes.anovaculinary.com/recipe/sous-vide-chicken-thighs-with-lemon-sauce/ .

1tbsp 0.015l 15ml 3tsp 0.063cup 0.026pint olive oil	heat in skillet on med-high				sear until well browned		serve
1tbsp 0.015l 15ml 3tsp 0.063cup 0.026pint butter for searing
900g 0.9kg 1.98lb 31.7oz chicken thighs	season	vac bag	sous vide 74degC for 2h	pat dry
salt for chicken
pepper for chicken
1tbsp 0.015l 15ml 3tsp 0.063cup 0.026pint butter for chicken
1 onion	chop finely	brown	simmer until thick glaze	remove from heat	whisk in slowly	season to taste
1tsp 0.005l 5ml ¹⁄₃tbsp 0.021cup 0.009pint butter for onion
235ml 0.235l 15 ²⁄₃tbsp 47tsp 0.993cup 0.414pint beef stock
65ml 0.065l 4 ¹⁄₃tbsp 13tsp 0.275cup 0.114pint lemon juice	whisk
2 egg yolks