I think if you only have 2 ingredients, cocoa butter and cocoa nibs, then 1 - 0.05 = 95% is the amount of nibs you have. So, we have a proportion of ounces to percentage:

where x = # of ounces of cocoa butter you need.

From here, we show the math work --> Proportions

If 2 proportions are equal to each other, then we have:

Numerator 1 * Denominator 2 = Denominator 1 * Numerator 2

Solving for Numerator 1 we get:

Numerator 1 = (Denominator 1 * Numerator 2) / Denominator 2

Evaluating and simplfying using your input values, we get:

x =

x =

x = 0.8421052631578947 ounces